Parashat Devarim is always read during the Shabbat prior to Tisha B’Av. Why is this? Because in this parasha Moses reminds us of the story of the ten spies, who caused a terrible crisis among the Children of Israel after delivering a misleading report about the land of Canaan. As a result of the events that happened after this, God decreed that the generation that had left Egypt would die in the desert. According to the sages, that decree was given on the night of Tish B’Av, the ninth of the Hebrew month of Av.
However, what is Tisha B’Av and what do we commemorate on this day? Tisha B’Av is a fast day, the only day in the Hebrew calendar (apart from Yom Kippur) in which we fast for a whole day. It is a day of mourning to commemorate many tragedies that happened to the Jewish people. Many of these tragedies occurred on the ninth of Av itself or very close to it. This year, Tisha B’Av falls this coming Saturday, July 22nd, but because of the Shabbat celebration, it is commemorated the following day, on Sunday.