Chazal prohibited studying most areas of Torah on Tisha b’Av since Torah “gladdens the heart” and it can distract a person from the requisite mourning. This prohibition applies also to women and children of age to appreciate the churban. It is customary to refrain starting from midday on erev Tisha b’Av since it can bring joy when continuing to think about those studies at night.
For this reason one may not study on Tisha bav about the korbanot
Torah sections including the korbanot that are part of the daily davening are subject to a halachic discussion if they should be recited and the custom is that are to be recited, since they are standard and don’t cause delight (e.g. eizehu mekoman, pitum haketores).
. However, the Mishnayos recited by mourners after Maariv and Shacharis should be from Moed Katan (or Taanis) without the additional passage by Rabbi Chananya ben Akashya.
One may learn sections of Torah that don’t cause delight. This includes the halachos of Tisha b’Av or mourning or sections of Gemara that discuss the churban or laws of mourning. The Rebbe Rashab would study each year the sections of Gemara and Midrash that discuss the churban. Even these sections should not be studied in depth (pilpul), which is delightful.
