Today’s page begins with a discussion on moving to or from a fast day when it abuts Shabbat. (There is a fantastic Mishnah on this page which opens another range of subjects. We’ll deal with that tomorrow).
The problem is that fasting is forbidden on Shabbat –it is a time of feasting, not fasting – a time of joy not affliction. So what happens when, say Tishsa b’Av occurs on a Friday? Do you go through with the entire day’s fast (complete it) and enter Shabbat Friday night a little afflicted, or do you break the fast before Shabbat begins so that you enter Shabbat with joy?
Rabbah further stated: When we were at Huna's we raised the question whether a student who kept a fast on the eve of the Sabbath must also complete it? He had no ruling on the subject. I appeared before Rab Judah and he also had no ruling on the subject.
‘Let us’, said Rabbah, ‘consider the matter ourselves. It was in fact taught: If Tisha b’Av fell on a Sabbath and, similarly, if the eve of Tisha b’Av fell on a Sabbath a man may eat and drink as much as he requires and lay on his table a meal as big as that of Solomon in his time. If Tisha b’Av fell on the Sabbath eve [food] of the size of an egg must be brought and eaten [before the conclusion of the day] so that one does not approach the Sabbath in a state of affliction’.
The story is told of Rabbi Akiva who did exactly that – one year when Tisha b’Av fell of a Friday, before the day concluded he sat with this students and sucked out a lightly roasted egg without salt – and did so to demonstrate this principle.
In fact it applies more broadly:
No fast day may be imposed upon the public on New Moons, Hanukkah or Purim,
But not everyone agrees with the principle of interrupting the fast to enter the holiday:
but if they began [the period of fasting prior to these days] there is no need to interrupt it; so R. Gamaliel.
But maybe Gamaliel did not mean that the fast had to be completed:
Said R. Meir: Although R. Gamaliel laid down that ‘there is no need to interrupt it’, he agrees nevertheless that [the fasts on these days] must not be concluded, and the same ruling applies to Tisha b’Av that falls on a Sabbath eve.
But, here’s the fun part:
And it was further taught: After the death of R. Gamaliel, R. Joshua entered [the academy] to abrogate his ruling, when R. Johanan b. Nuri stood up and exclaimed: ‘I submit that "the body must follow the head"; throughout the lifetime of R. Gamaliel we laid down the halachah in agreement with his view and now you wish to abrogate it? Joshua, we shall not listen to you, since the halachah has once been fixed in agreement with R. Gamaliel!’
And there was not a single person who raised any objection whatever to this statement.
Rabbis do battle for authority! And as to the answer to the actual question:
Mar Zutra made the following exposition in the name of R. Huna: The halachah is [that those] fasting [on a Sabbath eve] must complete the fast.