When the ninth of Av falls out on Shabbat, the fast is postponed to Sunday. On that Shabbat, we show no signs of mourning. Rather, we eat and drink like we do on any other Shabbat; one may even serve a meal as lavish as that of King Shlomo in his time (see above 9:4).²⁶

As we learned above (section 4), pregnant and nursing women must fast on Tisha Be-Av. If the fast was postponed, however, the law is more lenient: if they feel slightly weak or if they experience some type of pain, they are exempt from fasting, even though they are not actually sick (bhl 559:9, s.v. "ve-eino"; Kaf Ha-ĥayim 559:75).

The main participants at a brit mila must fast on Tisha Be-Av. However, the law is more lenient when the ninth of Av falls out on Shabbat and the fast is postponed to Sunday. According to most poskim, the main participants at a brit mila may pray Minĥa after midday, perform the circumcision immediately afterward, and then eat and drink. Some poskim rule stringently on the matter. In practice, the prevalent custom is to perform the brit mila toward the end of the fast and schedule the meal for after tzeit ha-kokhavim.²⁷

When the ninth of Av falls out on Shabbat and the fast is postponed to Sunday, the tenth of Av, the customs of mourning do not continue after the fast ends. Thus, one may get a haircut, do laundry, and bathe in hot water immediately after tzeit. However, many authorities maintain that one should refrain from eating meat and drinking wine that night. Since everyone fasted during the day, it is improper to rejoice immediately by consuming meat and wine (Rema 558:1, mb ad loc. 4-5, Hilkhot Ĥagim 29:9). Others are lenient and permit eating meat and drinking wine immediately once the fast ends (R. Ĥayim Vital, Pri Ĥadash, Torat Ha-mo’adim 11:8).