Friday, August 5, is Rosh Chodesh Av, which marks the beginning of the Nine Days. Ashkenaszi Jews refrain from several activities during this time period starting on this day. Sephardim, however, only start refraining at the beginning of the week of Tisha B’Av (shevua she’chal bo).
What about a year when Tisha B’Av falls out on Shabbos but is pushed off to Sunday (such as this year)? Is the previous week considered shevua she’chal bo? Or is Tisha B’Av considered to be on Sunday, which would mean that there effectively is no shevua she’chal bo?
The Mechaber (Shulchan Aruch Orach Chayim 551:4) writes that this matter is subject to a machlokes and appears to side with the view that there are no halachos of shevua she’chal bo if Tisha B’Av is pushed off to Sunday.
Many explain that the machlokes is based on how one understands the establishment of the fast of Tisha B’Av. The Gemara (Ta’anis 29a) says that the Beis HaMikdash began burning close to the end of the ninth day of Av and continued burning throughout the tenth day of Av. Rabbi Yochanan said, “Had I been in the generation when Tisha B’Av was established, I would have established it on the tenth day of the month since the majority of the Beis HaMikdash burnt on that day.” The Gemara says that the Rabbanan who established the fast on the ninth day of the month did so because they felt that it was better to establish the fast day on the day the tragedy began.
Some authorities believe the Rabbanan only argued for establishing the fast on the ninth of Av when it is possible to fast on this day. When it is not possible (i.e., when this day falls out on Shabbos), they agree with Rabbi Yochanan that the fast should take place when the majority of the Beis HaMikdash burned – on the tenth day of Av. Therefore, in a year when Tisha B’Av is observed on the tenth (because of Shabbos), the previous week is not shevua she’chal bo.
Other authorities – who maintain that the halachos of shevua she’chal bo do, in fact, apply to the week prior to Tisha B’Av when it is pushed off to Sunday – believe that the Rabbanan established the fast to always be on the ninth of Av, even when one cannot fast on that day. We fast on Sunday when the ninth falls out on Shabbos only to make up for not being able to fast on Shabbos. However, the fast day is really still on the nineth of Av. Therefore, all the halachos of shevua she’chal bo apply to the previous week since Tisha B’Av does, in fact, fall out during that week – namely, on Shabbos.
This explanation also accounts for another machlokes – between the Mechaber and the Rema (554:19) regarding whether one must keep aveilus betzina (hidden aveilus, i.e., refraining from marital relations) on Tisha B’Av that falls on Shabbos. The Mechaber says that one may have marital relations on the ninth day of Av when it falls out on Shabbos. We can assume this is because he maintains that the fast was primarily established to be on the tenth day, and the ninth day is not a fast day at all when it lands on Shabbos. The Rema argues that this is forbidden and that one must keep aveilus betzina. He does so presumably because he believes the Rabbanan established Tisha B’Av to always be on the ninth day of Av – even when one cannot fast.
However, there is a problem with explaining the machlokes in this manner. In 559:9, the Mechaber writes that someone who makes a bris milah on a Tisha B’Av that was pushed off to Sunday does not have to fast and may wash his body. He must fast, however, and may not wash his body if he is making a bris milah on the regularly scheduled day of Tisha B’Av. If the Mechaber, though, maintains that Sunday becomes the actual day of the fast (when Tisha B’Av falls out on Shabbos), and not Shabbos, why is he lenient?