Tu B’Av in the Mishnah
Mishnah Ta'anit Tractate 4:8
Rabban Simeon ben Gamaliel says, "Never were more joyous festivals in Israel than the 15th of Ab and the day of atonement, for on them the maidens of Jerusalem used to go out dressed in white garments—borrowed ones, in order not to cause shame to those who had them not of their own;” these clothes were also to be previously immersed, and thus they went out and danced in the vineyards, and they said: Young men, look and observe well whom you are about to choose [as a spouse]; regard not beauty [alone], but rather look to a virtuous family.” “Charm is deceptive, and beauty is fleeting; but a woman who fears the Lord is to be praised” (Proverbs 31:30) and says: “Honor her for all that her hands have done, and let her works bring her praise at the city gate” (Proverbs 31:31); and he said. Daughters of Jerusalem, 11 come out, and look you daughters of Zion.
Look on King Solomon wearing a crown, the crown with which his mother crowned him on the day of his wedding, the day his heart rejoiced” Song of Songs 3); “the day of his wedding” alludes to the day of the giving of the law, and “the day of the gladness of his heart” was the day that the building of the Temple was completed." May it soon be rebuilt in our days; Amen!