Although the prohibitions of Tisha BeAv are similar to those that apply on Yom Kippur, the restrictions of Tisha BeAv apply only by rabbinic law while Yom Kippur is decreed by the Torah. For this reason, Tisha BeAv is considered to be less severe a fast than Yom Kippur. Consequently, in some cases there is greater room for leniency regarding a sick person, a woman after childbirth, and a nursing woman. In any case, before adopting a leniency, one must consult a rabbi regarding each particular case.

All five prohibitions that apply on Yom Kippur also apply on Tisha BeAv: eating and drinking, bathing the body, anointing the body, wearing leather shoes, and engaging in marital relations.

Further reading: For more on the laws of Yom Kippur, see p. 163.

In order to increase the feeling of mourning on Tisha BeAv, several other prohibitions were added to the five basic restrictions of the day.

No Torah study: Studying Torah brings one joy and may cause a person to forget the sad, mournful mood of the day. Therefore, learning most sections of the Torah is prohibited on this day. According to some Ashkenazic halakhic authorities, the prohibition against studying Torah begins at midday on the eve of Tisha BeAv (the eighth of Av). Despite this restriction, it is permitted to study Torah topics that have a sad aspect, such as the book of Lamentations with its commentaries and midrashim, the book of Job, the parts of the book of Jeremiah that deal with the destruction of the Temple, as well as other midrashim and talmudic passages that focus on the destruction.

One may recite verses from the Torah that are included in the prayer liturgy. There are communities in which it is customary to postpone the recitation of several of these passages until the afternoon service, which is held after midday when mourning is not as severe. Likewise, some permit reading excerpts from the book of Psalms and the weekly Torah portion with its Aramaic translation after midday.

No sitting on chairs: From the start of the fast until midday on Tisha BeAv, one may not sit on a regular chair, but rather only on the ground or on a low stool, in the manner of a person who is mourning the passing of a family member.

No greetings: On Tisha BeAv one does not extend greetings to others. If one is walking in the street and a neighbor or acquaintance greets him absent-mindedly or due to a lack of knowledge, one may respond. He should do so in a soft voice and in a manner that emphasizes his state of sorrow and that he is uncomfortable with the exchange.

No distractions: As a general rule, the day of Tisha BeAv should be dedicated to reciting lamentations [kinnot] and thinking about the tragedy of the destruction of the Temple. It is inappropriate to deal with anything that might distract one from the solemn nature of the day. This means that one should not work or engage in various tasks, even if postponing certain activities might cause him a moderate financial loss.