אֵיכָה֩ יָעִ֨יב בְּאַפּ֤וֹ ׀ אֲדֹנָי֙ אֶת־בַּת־צִיּ֔וֹן הִשְׁלִ֤יךְ מִשָּׁמַ֙יִם֙ אֶ֔רֶץ תִּפְאֶ֖רֶת יִשְׂרָאֵ֑ל וְלֹא־זָכַ֥ר הֲדֹם־רַגְלָ֖יו בְּי֥וֹם אַפּֽוֹ׃ (ס)
How hath the Lord covered with a cloud The daughter of Zion in His anger! He hath cast down from heaven unto the earth The beauty of Israel, And hath not remembered His footstool In the day of His anger.
Mishneh Torah, Fasts
Torah scholars should not greet each other on the Ninth of Av. Rather they sit sadly and sigh like mourners. And if an ignorant person greeted them, they may return his greeting with a soft voice and a serious demeanor. And it is forbidden on the Ninth of Av to read the Torah, the Prophets, the Writings, the Mishnah, the laws, the Gemara and the aggadah. One may only read from Job, Lamentations and from bad things in Jeremiah. And we make the infants of the house of their teacher idle (we do not have them study). And some sages are accustomed to not laying the head tefillin.