Is there a Mitzva of Talmud Torah on the Ta’anis of Tisha B’av?
There is no obligation to learn Torah on the fast of Tisha B’av. The day is considered akin to aveilus; the mourner is exempt from Torah study. Consequently, there is no prohibition of neglecting Torah either (Rav Yoel Schwartz, Aveilus Hachurbon). Nonetheless, one should not waste time. We should not be distracted from the mourning of the day, and there are appropriate subjects which are permissible to learn.
If the mitzva of learning Torah does not apply to Tisha B’av, why do we say the brocha for Torah study? Birkas Hatorah is not simply a brocha for a mitzva. It is a mitzva in and of itself, expressing praise and thanks for the sacred Torah. This is why women say the brocha, even though they are not obligated in Torah learning — even according to those who do not allow brochos over non-obligatory mitzvos. (Rav Chaim Brisker in Chidushei Hagraz, Hilchos Brochos; Rav Shlomo Zalman Auerbach, Halichos Shlomo, Brochos, p. 75)
A Prohibition from the Rabbis
How can the Rabbonon take away a mitzva? Mourning for seven days is a rabbinic concept, and the laws of Tisha B’av are also d’rabbonon.
The truth is that the Rabbonon are able to tell us not to perform a mitzva at certain, limited times. For example, we may not sound the shofar when Rosh Hashana occurs on Shabbos, although from the Torah there is a mitzva. (Rosh Hashana 29b)
Learning on Erev Tisha B’av, During the Fast, Tisha B’av Which Falls on Shabbos
The Ma’amar Mordechai was concerned. Rema says that on Erev Tisha B’av as well, the minhag is not to learn Torah (except those subjects which are permissible on the fast). Many gedolim were lenient in this regard. The Ma’amar Mordechai felt that, even on Tisha B’av itself, perhaps it would be better to allow Torah study rather than waste time with frivolous conversation and foolish endeavor, which altogether takes the mind away from the tragedies of the day. He actually writes, that If he wasn’t afraid of the other Rabbonim, he might have permitted learning on Tisha B’av itself! Certainly, the day before the fast one could be lenient. (Biur Halacha, 553)
From here, it seems that it is surely appropriate to learn whatever is allowed for this day, whether there is a mitzva of Talmud Torah or not. However, on Erev Tisha B’av, many of the Rabbis concluded that it is overly stringent to forbid learning; certainly, when Shabbos precedes the fast, one is allowed to learn on Shabbos (even if the date is actually the ninth of Av). (Mishnah Brurah, 553) Rav Elyashiv concluded that on Shabbos before the fast, there is definitely a prohibition to neglect Torah study. (M’vakshei Torah, 47, p. 10)
How deeply may one learn? Technically, the learning that is permitted would be simple and straight-forward, avoiding depth. Some say, for example, not to learn Tosafos. But Rav Elyashiv said that one has to understand what is said, or it is not learning (therefore, one might need commentaries to answer his difficulties). The degree of depth depends on each person, he would say.
I heard years ago that being lenient in this regard can be a leniency which leads to a stringency — if one does learn with depth, he may get more involved with the feeling of the day. (The Zeditchov Rebbe of Chicago, Shlita)
As on all the fast days, the main mitzva is not the fast itself, but teshuva. We should contemplate our errors, and focus on practical corrections for our behavior. According to the Rambam (Hilchos Ta’anis, 5:1), on all fast days slichos are said. Our practice, however, is not to say slichos on Tisha B’av — see Tur and Beis Yoseif (Simon 559): it’s not a favorable day for prayers.
The fast of Tisha B’av is a time for crying. We cried unnecessarily at the time of the meraglim — we were punished that we would need to cry for the generations. Then — we had no reason to cry. Now — we have reason to cry: All the churbons, pogroms, shootings etc., which have occurred time and time again. Crying on Tisha B’av is the atonement, the fulfillment of the decree.
Why was it such a terrible thing to cry then? Moshe Rebbenu discusses the story of the meraglim in Parshas Devorim. In response to their fears, he says, “In this matter, you do not believe in Hashem…” (Devorim 1:32) To Rashi, the blame is for the disregard towards Hashem’s promise of conquering the land. To Ohr Hechaim, though, they are denying the daily miracles which Hashem did and continues to do for Klal Yisrael.