Because the mishnah positions the discussion of the 15th of Av directly after delineating the tragedies of the 9th of Av, it is clear that the theme of this holiday is meant to confront and oppose the negativity of the 9th of Av. All the reasons for the holiday correspond to some aspect of the 9th of Av:
The first tragedy of the 9th of Av was the decree that the generation of the desert would not be able to enter the Land of Israel. Opposing this is the joy of the 15th of Av, when the deaths of the Jews in the wilderness ceased. Beitar also fell on the 9th of Av, and opposing this is the relief on the 15th of Av several years later, when the slain of Beitar were brought to burial.
The full rebuttal of the decree against entering the Land of Israel is when the Jewish people fully settle in and take ownership of the Land. As long as the tribes were forbidden to intermarry, their ownership of the land was incomplete, for each tribe only could claim ownership of their portion. But once the members of different tribes were permitted to intermarry, then each member of each tribe could technically possess any parcel of the Land of Israel. Thus, this opening of intertribal marriage on the 15th of Av was the full consummation of Jewish ownership of the Land of Israel.
The primary tragedy of the 9th of Av, however, was the destruction of the two Temples in Jerusalem. The Second Temple, the sages taught, was destroyed because of needless hatred between Jews. To combat this essential tragedy, we need a holiday whose theme is twofold: the building and strengthening of the Temple and its service, and the love and connection between all Jews.
This was the day of the breaking of the scythe. The ultimate purpose of the Temple was to have a place where sacrifices could be brought to G-d. Thus, the preparation of wood for the entire upcoming year of sacrifices is an essential task for the functioning of the Temple. But there is also an element of love and generosity here. For the wood was to be used for every Jew, for their individual sacrifices or communal sacrifices, without distinction. This undifferentiated generosity is therefore a response to the hatred that was the cause of the Temple’s destruction.
The literal breaking of the scythe was an even greater expression of the fortification of the Temple. Iron, the sages taught, was “created to shorten human life,” while the altar, which offers forgiveness, was “created to lengthen human life.” The iron of the scythe was only tolerated as long as it was preparing wood for the altar. Once the wood-cutting season was over on the 15th of Av, the iron could no longer serve a positive purpose and so it was broken. This symbolized the endurance of the life-giving Temple and its altar, as opposed to the harmful force of “iron.”
This also explains why the 15th of Av was celebrated, as the mishnah explains, with the maidens of Jerusalem dancing in circles and borrowing clothes from each other: the circle emphasizes the undifferentiated unity between the Jewish people, as does the cycle of borrowing clothing from across the economic divide.
