Taanit 26B

נשתברו הלוחות, ובטל התמיד, והובקעה העיר, ושרף אפוסטמוס את התורה, והעמיד צלם בהיכל.

the tablets were broken by Moses when he saw that the Jews had made the golden calf; the daily offering was nullified by the Roman authorities and was never sacrificed again; the city walls of Jerusalem were breached; the general Apostemos publicly burned a Torah scroll; and Manasseh placed an idol in the Sanctuary.

בתשעה באב נגזר על אבותינו שלא יכנסו לארץ, וחרב הבית בראשונה ובשניה, ונלכדה ביתר, ונחרשה העיר.

On the 9th of Av it was decreed upon our ancestors that they would all die in the wilderness and not enter Eretz Yisrael; and the Temple was destroyed the first time, in the days of Nebuchadnezzar, and the second time, by the Romans; and Beitar was captured; and the city of Jerusalem was plowed, as a sign that it would never be rebuilt.

משנכנס אב ממעטין בשמחה. שבת שחל תשעה באב להיות בתוכה אסור מלספר ומלכבס, ובחמישי מותרין מפני כבוד השבת. ערב תשעה באב לא יאכל אדם שני תבשילין, לא יאכל בשר ולא ישתה יין. רבן שמעון בן גמליאל אומר: ישנה. רבי יהודה מחייב בכפיית המטה, ולא הודו לו חכמים.

Not only does one fast on the 9th of Av, but from when the month of Av begins, one decreases acts of rejoicing. During the week in which the 9th of Av occurs, it is prohibited to cut one’s hair and to launder clothes, but if the 9th of Av occurs on a Friday, on Thursday these actions are permitted in deference to Shabbat. On the eve of the 9th of Av a person may not eat two cooked dishes in one meal. Furthermore, one may neither eat meat nor drink wine. Rabban Shimon ben Gamliel says: One must adjust and decrease the amount he eats. R' Yehuda obligates one to overturn the bed and sleep on the floor like one in a state of mourning, but the Rabbis did not agree with him.