Taanit 12 – Fasting for part of a day

Can one accept on himself to fast for only a part of the day? Rav Chisda said that it is impossible: it is not considered a fast if he ate before the end of the day. Then what is the concept of a partial fast? Rav Chisda will answer one who was too busy to eat in the first part of the day, and then decided to accept the fast until the end of the day: such a fast is valid, and he is even allowed to say the special prayer "Answer us!" for the fast days.

But how about the laypeople accompanying the kohanim in bringing the sacrifices – they were fasting but not completing the fast, and nevertheless, it is called a fast? – Ravi Chisda answers, "They did it just to afflict themselves, but it is not an official fast." So then what about Rabbi Yochanan, who used to declare, "I am in a fast until I come home." – He was only doing this to avoid the social obligation of a meal at the house of the ruling prince. And yet, some say that there is a concept of partial fast having spiritual significance.

Rav Yehoshua visited the home of Rav Idi, and they made a special meal for him, a calf one-third grown. He said, "I can't eat; I am fasting." They told him, "Do this: cancel this fast and repay it later!" He answered, "My fast has a reason: I saw a bad dream. In that case, you cannot change the day since the fast must be on the day of the dream." That is true even on Shabbat, except that on Shabbat, one should not fast – so what does one do? Fast now, and then fast again on a weekday, to atone for his fasting on Shabbat.

Art: Joseph's Dream By Gaetano Gandolfi