(ו) חֲמִשָּׁה דְבָרִים אֵרְעוּ אֶת אֲבוֹתֵינוּ בְּשִׁבְעָה עָשָׂר בְּתַמּוּז וַחֲמִשָּׁה בְּתִשְׁעָה בְאָב. בְּשִׁבְעָה עָשָׂר בְּתַמּוּז נִשְׁתַּבְּרוּ הַלּוּחוֹת, וּבָטַל הַתָּמִיד, וְהֻבְקְעָה הָעִיר, וְשָׂרַף אַפּוֹסְטֹמוֹס אֶת הַתּוֹרָה, וְהֶעֱמִיד צֶלֶם בַּהֵיכָל. בְּתִשְׁעָה בְאָב נִגְזַר עַל אֲבוֹתֵינוּ שֶׁלֹּא יִכָּנְסוּ לָאָרֶץ, וְחָרַב הַבַּיִת בָּרִאשׁוֹנָה וּבַשְּׁנִיָּה, וְנִלְכְּדָה בֵיתָר, וְנֶחְרְשָׁה הָעִיר. מִשֶּׁנִּכְנַס אָב, מְמַעֲטִין בְּשִׂמְחָה:
(6) Five [calamitous] events happened to our ancestors on the 17th of Tamuz, and five on the 9th of Av. On the 17th of Tamuz, the tables of the Holy Law were broken; on that day the continual sacrifice ceased, and the city of Jerusalem was stormed; on it Opostamos burned the Holy Law, and placed an idol in the Temple. On the 9th of Av, it was decreed that our ancestors should not enter the Holy Land; on the same day the first and second Temples were destroyed, the city of Bethar was taken, and the city [of Jerusalem] was ploughed [like a field].
מקדש ראשון מפני מה חרב מפני ג' דברים שהיו בו ע"ז וגלוי עריות ושפיכות דמים ... אבל מקדש שני שהיו עוסקין בתורה ובמצות וגמילות חסדים מפני מה חרב מפני שהיתה בו שנאת חנם ללמדך ששקולה שנאת חנם כנגד שלש עבירות ע"ז גלוי עריות ושפיכות דמים
Due to what reason was the First Temple destroyed? It was destroyed due to the fact that there were three matters that existed in the First Temple: Idol worship, forbidden sexual relations, and bloodshed... However, considering that the people during the Second Temple period were engaged in Torah study, observance of mitzvot, and acts of kindness, and that they did not perform the sinful acts that were performed in the First Temple, why was the Second Temple destroyed? It was destroyed due to the fact that there was wanton hatred during that period. This comes to teach you that the sin of wanton hatred is equivalent to the three severe transgressions: Idol worship, forbidden sexual relations and bloodshed.
In a place where people were accustomed to perform labor on the Ninth of Av, one performs labor. In a place where people were accustomed not to perform labor, one does not perform labor. And in all places, Torah scholars are idle and do not perform labor on the Ninth of Av. Rabban Shimon ben Gamliel says: With regard to the Ninth of Av, a person should always conduct himself as a Torah scholar and refrain from performing labor. This is also taught in a baraita: Rabban Shimon ben Gamliel says: A person should always conduct himself as a Torah scholar, so that he will feel the hardship of the fast. It is taught in another baraita that Rabban Shimon ben Gamliel says: Whoever eats and drinks on the Ninth of Av, although the prohibition was instituted by the Prophets, it is as though he eats and drinks on Yom Kippur. Rabbi Akiva says: Whoever performs labor on the Ninth of Av never sees a sign of a blessing from that work. And the Sages say: Whoever performs labor on the Ninth of Av and does not mourn for Jerusalem will not see her future joy, as it is stated: “Rejoice with Jerusalem and be glad with her, all who love her; rejoice for joy with her, all who mourn for her” (Isaiah 66:10). From here it is stated: Whoever mourns for Jerusalem will merit and see her future joy, and whoever does not mourn for Jerusalem will not see her future joy. This is also taught in a baraita: Whoever eats meat or drinks wine in the meal before the Ninth of Av, about him the verse states: “And whose iniquities are upon their bones, because the terror of the mighty was in the land of the living” (Ezekiel 32:27).