When Tisha BeAv falls on a Sunday, or if the ninth of Av is a Shabbat and therefore the fast is postponed to Sunday, there are some changes in the manner in which the day is observed.

When the eve of the fast is Shabbat, the customs of mourning are not observed, and all food and drink is permitted at all the Shabbat meals, including the third meal in the afternoon. In such a case, one must be very careful not to continue eating and drinking beyond sunset.

One should not remove his leather shoes, nor display any kind of mourning until the conclusion of Shabbat. In many congregations, the evening service is delayed somewhat, so that the congregants can, at the end of Shabbat, say barukh hamavdil bein kodesh leĥol, “blessed is He who distinguishes between the sacred and the mundane,” and then remove their leather shoes. Some have the practice to also change out of their Shabbat clothes before going to the synagogue.

As on every other Saturday night, the passage of Ata honantanu (“You have graced us, etc.”) is added in the fourth blessing of the Amida prayer. Since it is prohibited to drink, Havdala is not performed over a cup of wine on Saturday night, but rather is postponed to the end of the fast on Sunday night. At the conclusion of the evening service, however, the blessing of “who creates the lights of fire” should be recited over a candle. Alternatively, it may be recited at home anytime on Saturday night following the conclusion of Shabbat and the recitation of the phrase: “Blessed is He who distinguishes between the sacred and the mundane.”

The next evening, upon the conclusion of the fast but before eating and drinking, Havdala should be recited over a cup of wine, and only the blessing over the wine: “who creates the fruit of the vine,” and the blessing: “who distinguishes between the sacred and the mundane,” are recited, without the introductory verses.

When the ninth of Av is a Shabbat and the fast is postponed to Sunday, its severity is somewhat reduced, and certain leniencies are possible when needed. Nevertheless, one should not rule leniently for oneself, but rather consult with a rabbi who will examine each case on its own merits.