Tu B'Av: Full Moon of Divine Love

Rabbi Shimon ben Gamaliel said: There were no days of joy in Israel greater than the fifteenth of Av and Yom Kippur. On these days the daughters of Jerusalem would go out in borrowed white garments in order not to shame any one who had none...The daughters of Jerusalem come out and dance in the vineyards. What would they say? Young man, lift up your eyes and see what you choose for yourself. Do not set your eyes on beauty but set your eyes on the family. “Grace is deceitful, and beauty is vain, but a woman that fears the Lord, she shall be praised” (Proverbs 31:30). And it further says, “Give her of the fruit of her hands; and let her works praise her in the gates” (ibid, 31:31)...

What is the special joy of the fifteenth of Av? Rav Yehuda said that Shmuel said: This was the day on which the members of different tribes were permitted to enter one another’s tribe, by intermarriage. It was initially prohibited to intermarry between tribes, so as to keep each plot of land within the portion of the tribe that originally inherited it. This halakha was instituted by the Torah in the wake of a complaint by the relatives of the daughters of Zelophehad, who were worried that if these women married men from other tribes, the inheritance of Zelophehad would be lost from his tribe (see Numbers 36:1–12). What did they expound, in support of their conclusion that this halakha was no longer in effect? The verse states: “This is the matter that the Lord has commanded concerning the daughters of Zelophehad, saying: Let them marry whom they think best; only into the family of the tribe of their father shall they marry” (Numbers 36:5). They derived from the verse that this matter shall be practiced only in this generation, when Eretz Yisrael was divided among the tribes, but afterward members of different tribes were permitted to marry. On the day this barrier separating the tribes was removed, the Sages established a permanent day of rejoicing.

Rabba bar bar Ḥana said that Rabbi Yoḥanan said: The fifteenth of Av was the day on which the deaths of the Jews in the wilderness ceased. The entire generation that had left Egypt had passed away, as the Master said: After the sin of the spies, on account of which the Jews of that generation were sentenced to die in the wilderness, as long as the death of the Jews in the wilderness had not ceased, God’s speech did not come to Moses, as it is stated: “And it came to pass, when all the men of war were consumed and dead from among the people, that the Lord spoke to me, saying” (Deuteronomy 2:16–17). This indicates that only then, after the last member of that generation had died, was God’s speech delivered to me, i.e., Moses, but not beforehand. When the Jews realized that the decree that God would not speak to Moses had been lifted, they established that day as a permanent day of rejoicing.

...therefore the fifteenth of Av is in the nature of a sweetening and a repair of the ninth of Av...