The Book of Genesis recounts several stories that involve dreams: Jacob sees a ladder with angels ascending and descending, Joseph dreams of his ascension to power, Pharaoh's steward and baker dream of their separate fates, and Pharaoh dreams about years of plenty and famine.
All these dreams were messages from G‑d. In fact, dreams are the medium through which G‑d would often communicate to the prophets.
Rabbi Schneur Zalman of Liadi explains that meaningful dreams emanate from a very high spiritual level; a level that completely transcends this physical world and can therefore feature supernatural events that completely defy logic.
But does this mean that our dreams, too, are messages from G‑d? Should we be frightened by a dream that portends doom?
The Significance of Dreams
Even an ostensibly bad dream can be turned into a good oneMost of our dreams today are not messages from G‑d; they're simply thoughts that are recycled from what occupied our minds during the day. Negative dreams experienced after stressful incidents can certainly be attributed to those incidents; they don't foretell anything bad.
It is a dream's interpretation that actually causes it to be fulfilled. In the words of the Talmud, "All dreams follow the mouth." Therefore, if one doesn't have his dream interpreted, it will not be fulfilled.
In addition, even an ostensibly bad dream can be turned into a good one if it is interpreted in a positive light. However, only someone with special intuition and insight can interpret dreams in this way.
The Rebbe was approached numerous times by people who were disturbed by their bad dreams. The Rebbe stated that unless the individual is of exemplary piety, his dreams are not messages from G‑d, and there's no reason to be concerned about them; rather he should simply not think about them. Nevertheless, if a person is nervous because of the dream, he should interpret it positively, give charity, check his tefillin and mezuzot to ensure that they are kosher, and/or strengthen his faith in G‑d and the observance of His Torah. Certainly if one has already recited the prayer at the time of the Priestly Blessing (see below), the dream has already been transformed to good and there's nothing more to worry about.
Nevertheless, if a person is troubled by a dream, our Sages have provided various ways to avert any evil decree that the dream may have portended.
One who has a bad dream may fast, for fasting has great power to avert potential bad decrees. The fast should be accompanied by repentance and disbursement of charity, as well as Torah study and prayer.
This fast is not obligatory; if the person is not concerned about the dream and considers it nonsense, he doesn't have to fast, especially today when dreams have less import than in earlier generations.
This fast is observed the day following the occurrence of the dream. In the event that the person is very distressed by the dream, he may fast on that day even if it is Shabbat or a holiday. In such a case, however, the person must fast again on the following day to atone for having fasted on a holy day. There are only two days a year when it's forbidden to fast a "dream fast": The day before Yom Kippur and Purim.
If one had a bad dream in the course of a daytime nap, and wishes to fast, he should do so from the moment he arises for the following twelve hours.
If one had a bad dream about someone else, the dreamer is the one who fasts.
Fasting has great power to avert potential bad decreesPlease note, that nowadays it is not common custom to fast following bad dreams. Aside for the fact that, as explained earlier, most dreams today are nonsense, in general voluntary fasts are discouraged. See Personal Fast Days for more on this topic.
Another way to transform a possible bad decree implied by a dream is to do a ceremony called Hatavat Chalom (lit. "making a dream good") on the day following the dream. The ceremony calls for the one who dreamt to go to three friends and recite various verses and prayers responsively. This prayer is printed in various prayer books (in the old Chabad siddur [Hebrew-only edition], it can be found on page 377).
If One Doesn't Remember the Dream
One who had a disturbing dream and doesn't remember its details, can "transform" it during the Priestly Blessing. As the kohanim sing before they recite the words of their blessing, a prayer – published in most prayer books – to transform these unknown dreams is recited. If the kohanim do not sing, the prayer may be said while they are saying the words of the blessing. The prayer should be completed just before the congregation responds "Amen" to the final blessing, thus the "Amen" is also in response to the individual's prayer.
One who lives in Israel, where the kohanim recite their blessing on a daily basis, should say this prayer immediately following a bad dream which he cannot recall. If one lives outside of Israel, where the kohanim only recite their blessing on the holidays, he should say this prayer when the chazzan says the words of the kohanim's blessing during the repetition of the Amidah.
In addition, everybody should say this prayer when the kohanim give their blessing on the holidays, for we presume that from one holiday to the next everyone probably had a bad dream which they then forgot. (See page 352 in the new Chabad prayer book for more details about this prayer.)
Vows Made During a Dream
If one recalls making a vow during the course of a dream, it is possible that it is a vow that G‑d is instructing him to make. He therefore should not disregard it, instead he should have it annulled. If possible, he should gather ten people (who at least know how to read Chumash) in order to perform the annulment ceremony. If one cannot do this, it is sufficient to annul it before a quorum of three. Even if the vow was annulled in the dream, he still must annul it as above, for it is possible that the first part of the dream had significance and the end of it did not.
Excommunicated in a Dream
When ten men are gathered, the Shechinah is presentIf a person dreams that he's been excommunicated, he must gather ten Torah scholars to annul the excommunication; it is possible that this was a message that G‑d was excommunicating him, and when ten men are gathered, the Shechinah is present and the excommunication can be annulled.
The following nocturnal visions are considered positive signs: A well, a river, a bird, a kettle, a donkey, a white horse, Ishmael the son of Abraham, Phinehas, King David, King Solomon, an elephant with a saddle, wheat, barley, a grapevine laden with grapes, a fig, a pomegranate, olives, an olive tree, dates, goats, a myrtle branch attached to its tree, a citron, a palm frond, a goose, chickens, or seeing oneself receiving a haircut, seeing one's jawbone fall out, having a boat ride, saying the Shema, responding to kaddish, or putting on tefillin.
One should look forward to the fulfillment of a good dream up to 22 years afterwards. We learn this from Joseph, whose dreams were only realized after 22 years.
Torah Insights Revealed
There are many recorded incidents of great Torah scholars who had Torah insights revealed to them in their dreams. Generally one may only decide halachic questions based on existing Torah sources, not on divine revelation; nevertheless, if the ruling received in a dream does not contradict those sources, some consider it valid. In fact, there was a Tosafist by the name of Rabbi Yaakov of Marosh who asked many questions via shaylat chalom, i.e., a question posed to G‑d for which one hopes to receive a response during a dream. Rabbi Yaakov received 89 responses via dreams; he recorded them and they are published under the title: Shailot U'teshuvot min Hashamayim ("Responsa from Heaven").
Instructions Received During a Dream
If someone received instruction during a dream regarding ownership of his property or similar matters, he's not obliged to comply. Nevertheless, we find that some rabbis heeded the advice they received in dreams.