A teaching for the month of Av (1), from Kalman Kalonymus HaLevi Epstein, Maor VaShamesh.
Hasket and listen, Israel; on this day you have become a nation. Deuteronomy 27:9
It is written in the Gemara that hasket means to bind together in fellowships (2), for cleaving to your fellows in one of the 48 ways in which Torah is acquired (3). Why? Because fellowship is the opposite of hatred, and we know that baseless hatred and factionalism were the cause of the destruction of the Temple in this very month many years ago (4). So in response we must strengthen ourselves in love, brotherhood, and fellowship more than ever.
1) The ninth of Av is the saddest day in the Jewish calendar, when we fast, sit on the floor, and recite the book of Lamentations as a way of showing our sorrow and regret over the destruction of both Temples on this day centuries ago. The nine days from the beginning of Av until the ninth are an extended period of mourning and repentance. 2) A pun is made between hasket and asu kitot; Berachot 63b. 3) Pirkei Avot 6:6 4) Yoma 9b