Introduction

The fascinating topic of dreams is discussed in scripture, Talmud, Midrash, Zohar, and Shulchan Aruch. A companion article on this web site, “Dreams – Aggadah” discusses the nature of dreams from the point of view of Aggadah to analyze the different types of dreams (viz. physical – psychological, spiritual – negative forces, and spiritual – angels). This article will discuss dreams from the point of view of Halacha quoting primarily from Shulchan Aruch and associated commentaries.     

Practices

The Shulchan Aruch (Orach Chaim) records the following rulings about dreams:

1. Prayer in presence of priests (kohanim) – 130.
2. Rectification of a dream – 220:1.
3. Fasting after a dream 220:2 (weekday) and 288:4-5 (Sabbath).

For each of these rulings the author will:

• Describe the practice.
• Provide its reason.
• Discuss the views of contemporary decisors of Halacha.  

Ruling 1 – Prayer in Presence of Priests (130)

Practice

Talmud

The Talmud (Berachot 55b) states that if someone had a dream and was unsure about it (either its contents or meaning), let him stand before the priests when they recite the priestly blessing (Numbers 6:24-26) and make the declaration below. The quote from the Talmud follows:

“Master of the Universe, I am Yours (divine) and my dreams are Yours. I have dreamt and do not know its meaning. Whether I have dreamt of myself (or others) or others have dreamt of me, if the dreams are good, fortify them like the dreams of Joseph. If the dreams require healing (because their portent is menacing), heal them like You (Hashem) healed the (bitter) waters of Marah by Moses our teacher (Exodus 15:22-25), like Miriam from her leprosy (Numbers 12:1-5), like Hezekiah from his illness (2 Kings 20:1-6), or like the (bitter) waters of Jericho by Elisha (2 Kings 2:19-22). Just as You (Hashem) transformed the curse of Balaam the wicked into a blessing (Deuteronomy 23:6), so transform all of my dreams for the best.”

The Talmud (ibid.) continues, “He should complete his prayer together with the priests so that the congregation responds amen both to the blessing of the priests and his individual request.”

The Talmud (ibid.) concludes, “If he finishes the above supplication before the priests complete their blessing he should say: Mighty One on high, Who dwells in power, You are peace and Your name is peace. May it be Your (divine) will that You bestow upon us peace.”

Shulchan Aruch

The Shulchan Aruch (ibid. 130:1) cites this Talmudic teaching and the Rema (ibid.) adds that in a place where the priests do not bless the people daily (e.g. Ashkenazi communities ibid. 128:44) the person should say recite this prayer when the cantor concludes the amidah with the blessing “Establish peace”. In this manner the congregation responds amen both to the blessing of the cantor and his individual request. By contrast in Sephardic communities the priests bless the congregants daily (ibid. 129:1). The Aruch Hashulchan 130:1 notes that if he knows that the dream portends of misfortune he may rectify the dream or fast (i.e. rulings 2 and 3 above).

The Shulchan Aruch (ibid.), based upon the Talmud (Berachot 55b), states that if one finished the above supplication starting with “Master of the Universe” before the end of the priestly blessing he should recite the following supplication which is similar to the one suggested by the Talmud:

“Majestic One on high, Who (divine) dwells in power. You (Hashem) are peace and Your name is peace. May it be Your will that You (Hashem) grant us and all of your people, the House of Israel, life and blessing for a secure peace.”   

The Aruch Hashulchan (Orach Chaim 130:2) notes that the Talmud states that “if not” he should recite the second supplication. This may mean if the congregant does not have time to recite the first supplication then he should recite the second one. However he concludes that the Shulchan Aruch follows the interpretation “if not” means that he has finished the first supplication and has time to recite both supplications.   

Since the priestly blessing consists of 3 scriptural verses the supplication starting with “Master of the Universe” is recited 3 times.  However the Talmud did not specifically mention recital of this supplication for each priestly blessing. Hence the Shulchan Aruch Harav (Orach Chdim130:1) writes that the congregants should recite the above supplication either at the conclusion of the first, second, or third verse of the priestly blessing. 

Insertion of Prayer

The codifiers of Halacha debate the optimal method of reciting the above supplications and the propriety of biblical reciting verses during the priestly blessing.

Supplications

To avoid the issue of distraction from the priestly blessings while reciting the above supplications, the Rema (Shulchan Aruch 128:45) writes that the priest elongate their song at the end of each of the 3 priestly blessings. In this manner the congregation pays full attention to the priestly blessings and recites the supplication while the priests are singing but not actually reciting the blessings. The Mishna Berurah (128:169) notes that the elongation of the song should not occur in the middle of the last word of the blessing. The Biur Halacha (on 128:45) explains that, according to current practice, after the cantor calls out the last word of each of the blessings, the congregation then recites the above supplications while the priests elongate  their song. After enough time to recite the supplications the priests conclude the priestly blessing. In this manner the congregation may recite the supplications without diverting attention from the priestly blessings. Alternately the congregation may recite the supplication when the priests elongate their song at the last letter of each of the 3 priestly blessings (Mishna Berurah 128:172).   

Biblical Verses

The Shulchan Aruch (Orach Chaim 128:26), based upon the Talmud Sotah 40a, states that when the priests bless the people the congregants shall remain silent and concentrate on the blessings. The Rema (ibid.) notes that the priests elongate their song when reciting the priestly blessings which allows the congregation to recite biblical verses in relation to each of the words of the priestly blessing. However the Rema (ibid.) recommends remaining silent and listening to the each of the words of the priestly blessing. Since there are conflicting views about reciting these verses many prayer books do include them with a comment about the propriety of recital during the priestly blessing.       

Mishna Berurah

The Mishna Berurah comments as follows:

Subsection 1 – The current practice in Ashkenazi communities is that the entire congregation recites this prayer during the priestly blessing whether or not they are aware of any dreams because this blessing is only recited on the major holidays (viz. Passover, Shavuot, Rosh Hashanah, Yom Kippur, Sukkoth, and Shemini Atzeret). Hence between these holidays it likely that each congregant had a dream.

The Biur Halacha (ibid.) notes that on the second day of the festival in the Diaspora, one should not recite this prayer unless he actually dreamt the night before because the prayer on the first day of the festival covers the previous dreams. However the current custom is to recite the prayer on both days to maintain consistency and to reflect the possibility of another dreaming about the one reciting the prayer. Hence the Biur Halacha suggests starting the prayer from the clause “Others have dreamt of me”.     

Subsection 4 – This prayer is omitted on the Sabbath unless the person actually dreamt an ominous dream the night before. Even though one does not normally recite supplications on festivals, dreams are an exception.

There is a dispute in the order of the clauses, “Whether I have dreamt of myself or others or others have dreamt of me”. The Mishna Berurah quotes the Magen Avraham (ibid. 130:2) who writes that the order of the first two dreams should be reversed (viz. “Whether I have dreamt of others or myself”). The Shulchan Aruch Harav (ibid. 130:2) explains that it is proper to pray for others before praying for oneself as the Talmud (Bava Kamma 92a) states, “When one prays on behalf of a friend and has the same need, he is answered with regard to his own need first.” However the Mishna Berurah notes that the Ashkenazi prayer books have the former text.

It is customary to end the supplication with the words, “May You (Hashem) protect me, be gracious to me, and favour me.”  These three words correspond respectively to the last words of the three verses of the Priestly Blessing, as follows: “protect me” paralleling the last clause of the first verse “protect you”, “be gracious to me” paralleling the last clause of the second verse, “be gracious to you”, and “favour me” paralleling the last clause of the third verse, “grant you peace”.  The Mishna Berurah writes that the ending of the supplication follows each of the priestly blessings (viz. “protect me” at the end of the first blessing, be gracious to me at then the end of the second blessing, and favour me at the end of the third blessing). However for purpose of simplicity the same ending is used for all of the blessings.       

Subsection 5 – The above supplications are recited for each of the 3 priestly blessings. However some prayer books include a Kabbalistic prayer, which begins with “May it be Your will” instead of “Master of the world” to be recited at the conclusion of the 3^rd priestly blessing. The Mishna Berurah presents both views and favours the former view.  

Subsection 6 – Some have the custom to recite the prayer starting with “Mighty One on High” when the cantor concludes the Amidah with the blessing “Establish peace”. By contrast the Shulchan Aruch states that one recites this supplication during the priestly blessing and only after reciting the supplication starting with “Master of the Universe”. However if there is not time for both, he only recites the first one.    

Subsection 9 – These prayers should not be recited every day. Rather only if one had a dream in the previous night. 

Reason

One recites the above supplications during the intervals of the priestly blessings because this is a propitious time for requests even though one should not recite supplications during the actual priestly blessings. A commentary on the Shulchan Aruch, Baer Hetev (Orach Chaim 128:45), explains that due to the ominous effects of this dream the Talmud permits reciting these supplications, albeit when the priests elongate their song and do not recite the words of the blessings.       

The verses follow (Numbers Chapter 6):

Verse 24 – “May Hashem bless you and protect you.”

Verse 25 – “May Hashem illuminate you with His presence (literally countenance) and be gracious to you.”

Verse 26 – “May Hashem elevate you with His presence (literally lift his countenance to you) and grant you peace.”

The Maharsha (Berachot 55b) explains that the 3 verses of the priestly blessing (i.e. protection, grace, and peace) allude to the 3 types of dreams (viz. spiritual – negative forces, psychological, and spiritual – angels). Specifically one needs protection from negative spiritual forces (or in the vernacular – face one’s demons). For psychological dreams one asks Hashem for grace to deal with the challenges of life. For angelic spiritual dreams one thanks Hashem for granting him peace of mind. In addition the Hebrew word for peace (שלום) is related to the Hebrew word שלם (completeness) alluding to the integration of body, mind, and soul. This is a striking example of the nexus of Halacha and aggadah.

Contemporary Halacha

The contemporary decisors of Halacha endorse this practice and therefore this declaration appears in most prayer books in the section of prayers for festivals (e.g. the Artscroll Siddur Nusach Ashkenaz – Third Edition on pages 696-700). 

By contrast Maimonides does not mention this practice in his code of Halacha (Mishneh Torah), either because he was not drawn to mystical practices even when cited in the Talmud or because of a possible loss of focus when reciting the above supplications during the priestly blessings. 

Maimonides writes (Laws of Prayers and Priestly Blessings 14:7), “The congregation should listen attentively to the blessing. They should stand face to face with the priests, without looking at their faces to avoid distraction.” On this ruling the Haggahot Maimuniyyot, a 13^th century halachic work on the halachic rulings of the scholars of Germany and France, writes (ibid. 14:5) that his teacher would recite the supplication starting with “Master of the Universe” at the end of the 3 priestly blessings. 

Rectification of a Dream (220:1)

Practice

Talmud

The Talmud Berachot 55b states that if someone had an ominous dream and is now distraught he should seek rectification of the dream in the presence of 3. He should say to them,” I had a good dream (even though he is troubled by the dream he should maintain a positive attitude).” They respond by saying, “The dream is good, let it be good, and may the Merciful One (Hashem). May they decree upon you from heaven 7 times that it will be good, and it will be good.” Afterwards they recite 3 verses of transformation (i.e. from bad to good), 3 verses of redemption, and 3 verses of peace.

The Talmud lists these verses as:

• Transformation – Psalms 30:12, Jeremiah 31:12, and Deuteronomy 23:6.
• Redemption – Psalms 55:19, Isaiah 35:10, and 1 Samuel 14:45.
• Peace – Isaiah 57:19, 1 Chronicles 12:19, and 1 Samuel 25:6.

Shulchan Aruch

The Shulchan Aruch following the Talmud Berachot 55b states that if someone had an ominous dream he should seek rectification of the dream in the presence of 3 of his friends. The Dirshu (note 5) comments that these 3 may be minors (i.e. less than 13 years old) if they know biblical Hebrew and study scripture.

The Shulchan Aruch then quotes the initial part of the ceremony verbatim from the Talmud and leaves the rest for the reader to read from the Talmud.

Mishna Berurah

The Mishna Berurah comments as follows:

Subsection 1 – One may use this rectification ceremony even if he is not sure that the dream portends misfortune.  

Subsection 2 – One should perform this ceremony in the morning because it is proper to fulfill a mitzvah without delay. The Aruch Hashulchan (220:4) allows the ceremony to occur before the morning prayers.    

Subsection 3 – One may perform this rectification on the Sabbath. It is praiseworthy to participate in this rectification because it provides solace to the troubled and is likened to healing a person.

Subsection 4 – The rectification should be repeated 3 times for emphasis. Other say it should be recited 7 times depending upon the interpretation of the expression “seven times”. At the conclusion of the rectification ceremony the 3 should recite the verse (Ecclesiastes 9:7), “Go, eat your bread joyfully and drink your wine with a merry heart, for G-d has already approved your deeds.”

The Kaf HaChaim (Orach Chaim 220:14) suggests that at the end of the ceremony the dreamer should give some money to the poor and the 3 should say, “Returning to Hashem, prayer, and charity nullify a harsh decree. Peace be unto you and all Israel, Amen”.    

Reason

This ceremony follows the Talmudic dictum (Berachot 55b) that dreams follow interpretation. Hence the Shulchan Aruch suggests choosing 3 friends who will aim to interpret the dream favourably. In addition the rectification ceremony may provide psychological relief to the dreamer.

The Maharsha (Berachot 55b) explains that the 3 types of verses (i.e. transformation, redemption, and peace) correspond to the 3 types of dreams respectively (viz. psychological, spiritual – negative forces, and spiritual – angels). Since the dream requires rectification it may contain elements of these 3 types of dreams. This is a striking example of the nexus of Halacha and aggadah.    

Contemporary Halacha

In contrast to the prayer in the presence of priests, many prayer books do not include this rectification procedure. The Dirshu edition of the Mishna Berurah (220:1) explains that at present most dreams are of the psychological type and do not warrant this procedure. In addition the dream may be a result of physical factors (e.g. overeating, toothache or similar malady, or events of the day) and not a message from heaven. Therefore the Aruch Hashulchan Orach Chaim 220:1 advises to ignore the dream and to follow the advice of King Solomon (Ecclesiastes 5:6), “Ignore dreams, vanities, and idle chatter; rather revere G-d.”    

 The author would like to suggest the following verse (Proverbs 12:25), “If there is worry in a man’s heart, let him remove it.” The Talmud (Yom 75a) advises the person to either remove the worry from his mind or tell his concerns to others to lower his anxiety. The first approach is suggested by contemporary decisors of Halacha to ignore the dream and put his faith in Hashem, study the Torah, and perform its mitzvoth. If he is still troubled by the dream he should discuss it with others who may advise him or if necessary perform the rectification ceremony.    

Fasting After a Dream (Weekday 220:2 and Sabbath 288:4)

Practice

Talmud

The Talmud (Shabbat 11a) states, “A fast is effective to neutralize a bad dream like fire burns chaff. It is specifically effective at daytime following the dream even on the Sabbath.” The Maharsha (ibid.) explains that just as fire quickly and completely burns chaff so too fasting may quickly and completely negate the dream which is compared to chaff.      

The Talmud (Berachot 31b) similarly says, “Anyone who fasts on the Sabbath (because of a dream) they (Heavenly tribunal) will annul a sentence of even 70 years. Nevertheless, they (Heavenly tribunal) hold him accountable for failing to delight in the Sabbath. What is his remedy (to make amends for this sin)?  He must observe an additional fast on a weekday (preferably on the next day to atone for the fast on Shabbat).” Rashi (ibid.) explains the great merit of this fast because everyone else is enjoying himself and he is fasting.

Shulchan Aruch

The Shulchan Aruch based upon the above citations from the Talmud states that:

• One may fast after a bad dream.
• Even on the Sabbath.
• After the Sabbath one must fast an additional fast.

Fast after a Bad Dream

The Shulchan Aruch (Orach Chaim 220:2) quotes the Talmud (Shabbat 11a), “A fast is effective to neutralize a bad dream like fire burns chaff.” The Rema adds, “Specifically on the following day and even on the Sabbath.”

Although Maimonides comments neither on the prayer in presence of priests (kohanim) nor the rectification of a dream he does rule in favour of fasting over an ominous dream as follows (Laws of Fasts 1:12):

“A person who has a disturbing dream must fast on the following day, so that he will be motivated to improve his conduct, inspect his deeds, and return to Hashem. He should undertake such a fast even on the Sabbath, reciting the passage Anenu (Answer Us) in each of the prayer services. When a person fasts on the Sabbath, he must fast on another day as well, to atone for nullifying the mitzvah of physically enjoying the Sabbath.”

The Mishna Berurah (220:6) comments that the fast will not be effective unless the person resolves to improve his connection with Hashem (viz. through Torah study and increased observance). Just as an offering to Hashem does not atone for sin without contrition; similarly a fast must be accompanied with contrition. King Solomon expresses the need for sincerity as follows (Proverbs 15:8 and 21:27 respectively), “The sacrifice of the wicked is an abomination to Hashem but the prayer of the upright is His will. The sacrifice of the wicked is an abomination, how much more so if he brings it with plans of wickedness!”  

Prayers

If someone decides to fast he should include the prayer for fast days (i.e. עננו – Answer Us) in his Amidah (Rema on Shulchan Aruch 562:5) on weekdays in the blessing קולנו שמע (Hear our voice), and on the Sabbath in the final supplication, My G-d guard my tongue א-להי נצור לשוני (Shulchan Aruch 288:6). The Mishna Berurah (288:7 and 22) explains the even though one may not make personal requests in the Amidah (e.g. livelihood or good health) on the Sabbath and festivals, the “Answer Us” prayer is different because it involves a confession over sin. In addition the Dirshu (288:30) comments that if the dream is truly ominous this confession is permitted to avert a decree from heaven.   

In addition one should recite the prayer “Master of the Universe “רבון כל העולמים” at the conclusion of the afternoon prayer whether fasting on a weekday or the Sabbath (Rema on ibid. 288:6).

This prayer based upon the Talmud (Berachot 17a) follows, “Master of the Universe, it is revealed (and known) before You (divine) that when the Temple was standing, if one sinned he offered a sacrifice. Although he only offered its fat and blood, the transgression is atoned for him (through Your (divine) abundant mercy). Now, I have engaged in a fast and my fat and blood have been diminished. May it be Your (divine) will that the diminution of my fat and blood be considered as if I offered it before You on the altar. May I find favour in Your (divine) eyes.”

(The words in brackets are in the prayer but not included in the Talmud except for the references to the divine.)                  

Even on the Sabbath

The Shulchan Aruch (Orach Chaim 220:2 and 288:4) allows one to fast after an ominous dream even on the Sabbath and festivals and certainly on minor festivals, for example Hanukkah and Purim (ibid. 568:5). The Mishna Berurah (288:7) adds that the person fasting should spend the entire day in Torah study and prayer.

Appendix 1 discusses the propriety of fasting after an ominous dream on other festive days due to their special nature.

Additional Fast

The Shulchan Aruch (ibid. 288:4), based upon the Talmud Berachot 31b, rules that after fasting on the Sabbath one should fast on the next day to atone for not fulfilling the mitzvah of physically enjoying the Sabbath. The Aruch Hashulchan (ibid. 288:7) explains that perhaps the dream was not a message from Hashem and the person missed the opportunity to delight in the Sabbath without sufficient cause. If a person is weak and cannot endure two consecutive daytime fasts he may select another day for fasting.

The requirement to fast an additional day also applies to the major festivals (e.g. Passover, Shavuot, and Sukkoth) and the minor holidays (e.g. Hanukkah and Purim) (Shulchan Aruch ibid. 568:5).  The Mishna Berurah (568:37) comments that this requirement of an additional fast only applies to holidays. Therefore fasting on propitious days when the supplication of tachanun is not recited (e.g. 33^rd day of the Omer) does not warrant an additional fast.

The Rema (ibid. 288:4) rules that the additional fast is postponed if the day following the Sabbath is a holiday whether major or minor. The Mishna Berurah (288:8) presents conflicting views about the need for an additional fast when Sunday is a mandated fast day to commemorate the tragedies surrounding the destruction of the temple and Jerusalem. He concludes that if weak one may be lenient and use the one fast for both purposes. 

Reason

As mentioned in the Talmud (Shabbat 11a and Berachot 31b), one is permitted to fast after an ominous dream to overcome a heavenly sentence. However for the fast to be effective the person must sincerely return to Hashem.     

Contemporary Halacha

Fasting on a Weekday

The contemporary decisors of Halacha advise against fasting after an ominous dream because of the following reasons:

• Since most dreams are of the psychological type and not a message from heaven they do not warrant fasting (Dirshu 288:27). In addition the dream may be caused by physical factors (e.g. fasting, overeating, thinking about events of the day, or a medical condition Shaar Hatziyun 220:1 and Dirshu 220:2-3). Although the Zohar (3:105b) advocates fasting after an ominous dream perhaps this approach applies to students of the Zohar whose lives are more spiritual than the norm. Therefore their dreams may be a message from heaven.     
• We are not expert in interpreting dreams. Dreams that appear as foreboding may be indicative of good fortune (Shulchan Aruch Orach Chaim 288:5).    
• Fasting is not recommended unless the person will find relief in this approach and is confident that the fast and introspection will be productive. In addition the person should realize that fasting may be counterproductive since it will interfere with his work and Torah study. In any event, the person should not brood over the dream and feel depressed (Yalkut Yosef 220:3).
• Excessive fasting may weaken the person physically and psychologically leading to paranoia or depression (Yalkut Yosef 220:4 and note 41). 
• Alternate approaches to fasting, as explained below, help to rectify the dream.

The reader may ask, “How could contemporary decisors of Halacha recommend against fasting over an ominous dream when the Shulchan Aruch permits it?” In addition to the reasons cited this fast is only permissible but not mandatory (Baer Hetev ibid. 220:3 quoting the Rashba). Since fasting is discretionary the contemporary decisors of Halacha rule that the potential benefits of fasting are overweighed by the drawbacks.

Therefore the Aruch Hashulchan Orach Chaim 220:1 advises to ignore the dream and follow the advice of King Solomon (Ecclesiastes 5:6), “Ignore dreams, vanities, and idle chatter; rather revere G-d.”

Alternate Approaches to Fasting

Based upon the Midrash (Ecclesiastes Rabbah 5:4 on verse 5:6) many suggest the following plan of action after being troubled by an ominous dream:

• Prayer – praying, crying, and entreating.
• Charity – according to his means. The Mishna Berurah (220:5) rules that pregnant and nursing women give money to charity in lieu of fasting. By extension if one does not fast after an ominous dream he should give some money to charity.
• Return to Hashem – separate from the object of sin.

(The author has included the comments of Maimonides (Laws of Returning to Hashem 2:4) on these 3 actions.)

It is interesting to note that these 3 actions are cited by the Talmud (Rosh Hashanah 16b) and the High Holiday prayer book to overcome a decree of punishment (in the language of the Midrash. By changing his actions to become a better person Hashem may nullify the decree.

In addition to the 3 primary actions listed above the Midrash (ibid) suggests the following changes if required:

• Name – become a different person and not the same one who sinned.
• Action – to change behaviour to the good and seek the path of righteousness.
• Place – exile causes a person to be humble.  

Reciting the Shema

The Talmud (Berachot 5a) states that one who recites the Shema (Deuteronomy 6:4-9) before going to bed holds a virtual  double-edged sword guarding him from evil as it is stated (Psalms 149:5-6), “Let the devout exult in glory; let them joyously sing upon their beds. Lofty praises of G-d (i.e. Shema) are in their mouths and a double-edged sword in their hands”. In addition the Talmud (ibid.) states that one who the Shema at this time keeps demons (e.g. psychological or spiritual) away from him. In this manner the nighttime Shema focuses a person on unity of Hashem (Deuteronomy 6:4), love of Hashem (ibid. 6:5), and study of the Torah (ibid. 6:7) enabling him to have dreams with a positive spiritual nature (in the language of the Talmud – Berachot 55b dreams inspired by angels).   

Fasting on the Sabbath

In addition to the objections of fasting on a weekday after an ominous dream, the decisors of Halacha strongly object to fasting on the Sabbath after a dream because the Sabbath should be physically enjoyed. The prophet Isaiah (58:13) specifically mentions that the Sabbath should be a delight, “You shall call the Sabbath a delight to the honour of Hashem.” Hence the potential benefit of fasting is overweighed by the mitzvah of delighting in the Sabbath.

The Zohar (2:207a) pictures these counterbalancing factors (i.e. fasting vs. delighting in the Sabbath) as two spiritual forces at the heavenly court. The court rules in favour of the one who fasts because he desires to neutralize the heavenly decree and in general does delight in the Sabbath. As explained above the fast may apply to students of the Zohar whose lives are more spiritual than the norm. Therefore their dreams may be a message from heaven.   

Maimonides (Laws of Sabbath 30:7), based upon the Talmud Shabbat 118b, explains that that a person must consume a particularly sumptuous dish and a pleasantly flavored beverage for delight of the Sabbath. However all of this must be done within the context of a person’s means. In addition Maimonides, based upon the Talmud Shabbat 117b, writes (Laws of Sabbath 30:7) that one should partake of 3 meals on the Sabbath (viz. one at night and two in the daytime).  Hence fasting on the Sabbath goes against both the spirit and laws of the Sabbath unless there is a great need.

In fact the Shulchan Aruch (Orach Chaim 550:3) rules that all of the historic public fasts that relate to either the destruction of Jerusalem and the temple or Jewish sovereignty over Israel are postponed to the next day when the historical date occurs on the Sabbath (i.e. 17^th of Tammuz,  9^th of Av, and 3^rd of Tishrei). The Mishna Berurah (550:8) notes that based on our current calendar the 10^th of Tevet cannot occur on the Sabbath. Since the fast of Yom Kippur is biblical (Leviticus 23:29) it overrides the prophetic command to enjoy the Sabbath. 

A person may fast only if the fear of the dream overrides the potential enjoyment of the Sabbath (Mishna Berurah 288:15). In addition the Mishna Berurah (288:20) comments that one should not fast on the Sabbath unless the portent of the dream is life threatening and not a loss of money. If one chooses to fast on the Sabbath after an ominous dream he should spend the entire day in the synagogue. In addition to the daily prayers he should recite Psalms, study the Torah and avoid idle chatter. In fact this recommendation applies if the person does not fast (Yalkut Yosef 220:4).

The Aruch Hashulchan (ibid. 288:13) advises a person to discuss the dream with his rabbi or mentor to both interpret the dream and determine the best course of action in lieu of fasting.    

Appendix 2 discusses the several points about fasting after an ominous dream on Shabbat.    

Conclusion

This article discussed dreams from the point of view of Halacha with respect to the following practices:     

1. Prayer in presence of priests (kohanim).
2. Rectification of a dream.
3. Fasting after a dream whether on a weekday or the Sabbath.

For each of these rulings the author:

• Described the practice.
• Provided its reason.
• Discussed the many views of contemporary decisors of Halacha.  

The applicability of these 3 practices hinges whether or not the dreams are a message from heaven or psychological. If the former is true then these practices apply otherwise the dream may be disregarded. In effect the decisors of contemporary Halacha conduct a spiritual cost/benefit analysis with respect to the value of the dream.

Since the first practice involves individual prayer most authorities permit it provided that the congregants listen attentively to the priestly blessing. The rectification of a dream involves the co-operation of others therefore the decisors of Halacha permit this practice but do not encourage it. Hence many prayer books do not include this ceremony. The decisors of Halacha rule against fasting after a dream because the cost (e.g. loss of functioning whether at work or Torah study) overrides the potential benefits, especially since the dream may not be a message from heaven.             

Appendix 1 – Fasting on Propitious Days

The decisors of Halacha debate the propriety of fasting on the days listed below due to their special nature. The Shulchan Aruch (ibid. 568:5) allows fasting on the day before the Day of Atonement and Purim. The Rema does not allow fasting on these days. Neither the Shulchan Aruch nor the Rema comments on fasting on Shavuot. As a compromise between the two positions the person should partake of one meal in the late afternoon thereby fulfilling the requirement of fasting and partaking of a festive meal. The dates and reasons follow including the sources:

• Shavuot – Fasting on Shavuot is a matter of dispute (Dirshu 494:17). On one hand the Talmud (Pesachim 68b) states one should partake of a festive meal on Shavuot to express gratitude to Hashem over the revelation at Sinai and giving of the Torah and therefore one should not fast on Shavuot (Shulchan Aruch Harav 494:18) . On the other hand the Talmud (ibid.) mentions the Sabbath and Purim as days on which one should not fast and the Shulchan Aruch allows fasting on these days (ibid. 288:4 and 568:5 respectively). Hence this citation from the Talmud is not conclusive and the requirement to partake of a meal may be overridden by concern over the dream. The Mishna Berurah (494:11), referring to his decision about fasting on the before the Day of Atonement, suggests that the person should skip breakfast and lunch and eat only one meal near the end of Shavuot.     
• Day before Day of Atonement (Rema ibid. 604:1) – Since it is a mitzvah to eat on this day (Shulchan Aruch ibid.) one should not fast. The Mishna Berurah (604:2) comments that if a person is particularly troubled about the dream he should skip breakfast and lunch and eat only one meal before the Day of Atonement. The Mishna Berurah (ibid.) suggests that if one decides to eat fully on this day he should select one day after the Day of Atonement to fast.
• Purim – The Rema (ibid. 695:2) rules that one should not fast over an ominous dream on Purim because this day is for rejoicing and feasting (Esther 9:22). Similar to the day before the Day of Atonement, the Mishna Berurah (695:6) suggests that if a person is particularly troubled about the dream he should skip breakfast and lunch and eat only one meal near the end of Purim. 

Appendix 2 – Fasting on the Sabbath

The Halacha discusses the following points about fasting after an ominous dream on Shabbat:

• Type of dream.
• Frequency of occurrence.

Type of Dream

The Shulchan Aruch (ibid. 288:5) considers the following dreams as ominous whether from the Talmud or other sources:

• Talmud – wild animal, a destructive tool, and book of Job (Berachot 57b).  
• Other sources – One who sees a burning Torah scroll or tefillin, or the final prayer service on the Day of Atonement called (Neilah), or falling items (e.g. beams of his house or his teeth). 

However these last 2 dreams may not indicate misfortune because the prayer service may be a good omen indicating that the dreamer’s sins are forgiven. In addition the Talmud (Berachot 57a) interprets falling items as sign of expansion meaning that his wife will give birth and he will need to expand his house. Hence we see the difficulty of interpreting dreams with certainty.    

The Talmud (Berachot 55b) considers the following dreams as significant:

• Early morning – After the evening meal, a person’s mind is more receptive to heavenly communication because the food has been fully digested.     
• A dream about someone else is significant because a person thinks more about himself than others. 
• Repeated dream – A dream that is repeated is significant because it implies urgency of the message similar to the dreams of Pharaoh (Genesis 41:32).   

Frequency of Occurrence

The Shulchan Aruch (ibid. 5) states one should not fast on the Sabbath unless the dream occurs at least 3 times to establish a pattern and gives a person some degree of confidence to downplay the significance of a dream unless it persists. To fast on a weekday only one occurrence is sufficient (ibid. 220:2).