Daf Yomi - Megillah 5 - Asarah b'Teves on Shabbos

The Mishna states that if Tisha b’Av would fall out on Shabbos, the fast would be postponed until Sunday. Rashi says that the same halacha would apply if the Seventeenth of Tammuz or the Tenth of Teves would fall out on Shabbos; its observance would be postponed until Sunday. The Mishna made special mention of Tisha b’Av since it was the only fast that was compulsory in those times.

The Avudraham writes that all of the fasts could fall out on Shabbos and when that happens, they will be postponed; however, the Tenth of Teves can never occur on Shabbos. It could fall out on Friday and we would fast on Friday. The Avudraham concludes that if the Tenth of Teves would fall out on Shabbos, we would observe the fast on Shabbos and it could not be postponed. This is based on a verse in Yechezkel which states: b’etzem hayom hazeh etc. - on this very day, and since the prophet specifies the precise day in this manner, we cannot postpone the fast.

Rashi clearly does not subscribe to this viewpoint. In his explanation of the Mishna, Rashi states that Tisha b’Av, the Seventeenth of Tammuz and the Tenth of Teves would all be postponed to Sunday if they would fall out on Shabbos.

The sefer Iturei Megillah explains the Avudraham. The reason that we do not observe a fast on Shabbos is because there is the option of fasting the following day as a replacement for the fast on Shabbos. The Avudraham maintains that there is no such possibility by the Tenth of Teves (similar to Yom Kippur) and the fast must be observed on that day. This explanation is said in the name of Reb Chaim Brisker as well.

The Chasam Sofer offers a different explanation. He states that one does not fast on Shabbos for a calamity that has happened in the past. However, one who is compelled to fast on account of a succession of bad dreams would fast on Shabbos since he is fasting in order to prevent a tragedy from transpiring. A fast, such as Tisha b’Av or the Seventeenth of Tammuz are fasts which commemorate episodes of the past and if they would fall out on Shabbos, the fast would be postponed. The Chasam Sofer states that the fast on the Tenth of Teves is fundamentally different from all the other fasts. He explains that in the year that the Beis Hamikdosh was destroyed, Hashem had decreed on the Tenth of Teves beforehand that there will be a destruction. The Gemora states that any generation that does not have the Beis Hamikdosh built in is regarded as if they destroyed the Beis Hamikdosh. Every year, on the Tenth of Teves, there is a judgment from Hashem if the Beis Hamikdosh will be built this year or not. We are fasting on the Tenth of Teves not on the account of the past, but rather for the future. This fast can be observed on Shabbos.

An interesting aside: The Chasam Sofer (O”C 9) concludes a responsa by signing his name and dating it Sunday, the 11th of Teves 5578. Was the Tenth of Teves on Shabbos that year?

In the Likutei Heoros on the Chasam Sofer, he comments that the Tenth of Teves cannot fall out on Shabbos and in the year 5578 it happened to be a Friday, so there seemingly is a printers mistake and it should say Sunday, the twelfth of Teves.