And he dreamed, and behold a ladder set up on the ground and its top reached to heaven; and behold, angels of God were ascending and descending upon it. (Genesis 28:12)
Dreams appear to play a prominent role in the next set of narratives in the Torah. Yet while the dreams reported in the Torah are clearly a type of prophecy, it is less clear whether our own, modern day dreams carry any spiritual significance.
The Talmud indicates that some dreams are insignificant and meaningless (Horayot 13b) whereas others have the potential to contain prophetic messages (Berachot 57b). Nevertheless, the even those dreams which carry some significance will always contain an admixture of truth and falsehood (Genesis 37:10 and Rashi ibid.).
Rabbi Moshe Chaim Luzzatto (d. 1746) describes three types of dream. The first is caused by food and indigestion, the second by the thoughts and experiences playing on one’s mind and the third which comes from the soul and may have prophetic significance. He explains that when we sleep, our souls are more loosely connected with the physical world they can, on occasion interact with spiritual forces (Derech HaShem 3:1:6).
Since there is no objective way of knowing whether even part of a dream contains a genuine insight, we cannot attribute any significance to information derived from dreams. Nevertheless, if a dream has a halachic implication the Shulchan Aruch (code of Jewish law) rules that we should be strict in cases of doubt (Yoreh Deah 210:2).
If someone had an especially disturbing dream, Maimonides (d. 1204) writes that they should fast the next day, even if it is Shabbat on which it is normally forbidden to fast (Mishnah Torah Laws of Fasts 1:12). The Shulchan Aruch also advises that they should recite certain verses in front of three friends to nullify the influence the dream may have (Orach Chaim 220:1). The Gemara explains that while the information in the dream may be meaningless, the interpretation is critically significant. We must therefore interpret dreams favourably even though we do not necessarily know what they mean (Berachot 56b).