Jewish fast days, known as a “ta’ana,” play a significant role in the Jewish calendar, serving as occasions for reflection, repentance, and spiritual introspection, each with their own meaning and historical basis. While fasting on these days is a solemn practice, it is notable that they are (almost) never held on Shabbat. This stems from both scriptural and halachic considerations (i.e from Jewish law), that can be better understood by learning about the nature of public fast days as well as Shabbat.
In the Torah, specifically in the Book of Exodus (31:13-17), there is a clear commandment regarding the observance of Shabbat. It is described as a sign between God and the children of Israel, a day of rest and sanctification. The verses emphasize that whoever violates the sanctity of Shabbat shall be put to death. While this may seem like it only represents a sort of solemnity, it also holds positive commandments to be joyful, and to eat nice food. The importance of Shabbat is hard to overstate, and included in that is not sorrow and withholding food.
Fasts on Shabbat
Halachically, the prohibition of fasting on Shabbat is derived from the Talmud (Oral Torah), where the rabbis discuss various actions that are not in line with the joy and delight that should characterize the Sabbath. That means even if one would want to fast for any reason, that would certainly not be permitted, and all rabbinic fast days are not held on Shabbat. In the case that it would fall on Shabbat, the fasting and all related prayer, relevant Torah readings etc. are pushed off onto the next day (Sunday) usually or Thursday in case the Fast of Esther would then land on the holiday Purim.
The halachic mechanism that allows for this exemption is based on the principle of “Oneg Shabbat,” the commandment for enjoyment and delight of the Sabbath. Fasting is incompatible Shabbat, but even further the calendar is usually configured to not allow public fast days on a Friday either, so that one will enter into Shabbat with joy and not hunger. This is not as strict, and the only exception to this is the fast of Asara B’Tevet when it occasionally falls on a Friday.
There is a notable exception to this rule on Yom Kippur, the Day of Atonement. Yom Kippur is the only fast day that is never “nidche l’shabbat” – it is observed even if it falls on Shabbat. This exception is rooted in the unique status of Yom Kippur as the holiest day in the Jewish calendar, surpassing the usual restrictions associated with Shabbat observance and unlike the other fast days which all are associated with mourning for a particular historical tragedy, Yom Kippur is actually a day of joy. Moreover, it is the only fast that is a Torah commandment and not a rabbinic decree.
In the year 2024 (corresponding to the Jewish year 5785), Yom Kippur will fall on Shabbat. Despite the general rule that fast days are not observed on Shabbat, Yom Kippur maintains its exceptional status, and the fast will be observed on Shabbat in accordance with Jewish tradition.
This nuanced interplay between scriptural commandments, halachic principles, and exceptions highlights the careful balance within Jewish law, seeking to maintain the sanctity and joy of Shabbat while acknowledging the unique significance of Yom Kippur in the Jewish calendar. Other days, important in their own right, cannot diminish the joy of Shabbat.