Shabbos is the ultimate day of Dveikus where we cleave to Hashem. Therefore, when Tisha B’Av falls on Shabbos we observe Tisha B’Av on the next day. We eat regular meat meals and we wear our regular Shabbos clothing.
This entire notion should enhance our appreciation of what Shabbos truly is all about.
It is proper to bring one’s crocs or tennis shoes and one’s lower stool to shul on Friday, as we cannot prepare on Shabbos for Motzei Shabbos.
There is a debate as to whether one can study the regular Pirkei Avos on Shabbos afternoon after Chatzos. It is best to be stringent. The review of the weekly Parsha should also be done before Chatzos.
Our Seudah HaMafsekes is held on Friday, not on Shabbos. The fast, in terms of eating, begins at Shkiya on Shabbos. The other issues of handwashing and shoe wearing begin at nightfall. Our shoes are removed right after Barchu and we sit on the floor not on a regular chair.
Havdalah is said in Maariv and then on Sunday night on a cup of wine. The Borei Meoirah HaAish is said on Saturday night. No Bsamim bracha is recited. Women should say Baruch HaMavdil Bain Kodesh l’Chol.
On Friday, one should only shower with hot water if one is finicky. Otherwise warmer water may be added to remove the chill. The shower should be shortened if possible.
The custom is not to study after Chatzos on this Friday as well.
Pregnant women do not have to fast on this day according to the Biur Halacha. People who are slightly ill as well do not have to fast. The fast does not have to be made up. A bris should be held in the afternoon and the Baalei Bris eat as well.
This is because the fasting we do on Sunday is a Nidcheh fast. The main day was still on the ninth of Av.
Laundry and showering may be done Sunday night. Eating meat and listening to music is permitted on Monday noon.