Siman 555

Even though in several matters the law of Tisha B'Av is like a mourner, nevertheless, the sages did not obligate on Tisha B'Av the overturning of the bed and the wrapping of the head like a mourner, for specifically regarding the negative commandments of mourning are they obligated on Tisha B'Av, such as: Torah study, washing and anointing, the wearing of shoes, and marital relations. But not the positive commandments of mourning, like the overturning of the bed and the wrapping of the head (Tur). And that which we do not don tefillin—this is not mentioned in the Gemara. The Rosh at the end of Ta'anit wondered at this: Behold, even a mourner is only forbidden on the first day? And there are some of the great authorities who donned tefillin in the morning in their homes, and recited Keriat Shema and removed them, and went to the beit knesset (Ba'er Heitev in the name of the Maharam Galante). And they say that so did the Arizal.

But all of Israel have the custom not to don tefillin and tzitzit in the morning at the time of the prayer. And the reason seems clear, for behold, the reason a mourner is exempt from tefillin on the first day is because it is written (Amos 8:10): "and the end thereof as a bitter day," and the primary bitterness of mourning is the first day. Therefore, one should not wear tefillin, which are called "pe'er"; and it is a kal vachomer on Tisha B'Av, the bitter and precipitous day for all of Israel, that we should not bear the pe'er of tefillin. And so too tzitzit, as it is written (Lamentations 2:17): "He has fulfilled [bitza] His word." And it is found in the Midrash (Vayikra Rabbah parsha 6) and in the Targum: "He tore His purple garment [porfira]" (Tur). Rather, we wear a tallit katan under one's clothes without a berakhah. And at Mincha we don tzitzit and tefillin, and recite the berakhah over them, and so all of Israel have practiced. And the tefillin of our teacher Tam – one should not don them on Tisha B'Av, even at Mincha. And some do don them (see Sha'arei Teshuva). And why do we don them at Mincha? Because at Mincha we receive consolations, as we say "Nachem."

And even though we do not practice the overturning of the bed, nevertheless our custom is to sit on the ground, or close to the ground, and not on a bench—until midday. And there is one who practices lying on the night of Tisha B'Av inclined on the ground, and places a stone under his head, but not every person is able to do so. However, in any event, a person should distress himself a bit regarding the matter of his bedding on the night of Tisha B'Av, such that if he was accustomed to sleeping with two pillows—he should sleep with one pillow. And some place a stone under their heads, in memory of what was said (Genesis 28:11): "And he took from the stones of the place," as it is brought in the Midrash: that he saw the destruction. However, the weak and pregnant women, who do not have the ability to distress themselves—should not do any of these. But in general, a person should diminish his honor and his pleasure on Tisha B'Av, in whatever way possible.