Every year on Tisha B'Av many Jews fast in remembrance of the destruction of the First Temple. Also known as "The Ninth of Av," the holiday falls on the ninth day of the Hebrew month of Av. In addition to the destruction of the Temple, it also commemorates a number of other tragedies that have befallen the Jewish people on the 9th of Av. For instance, on this day in 1290 the Jews were expelled from England and in 1492 they were expelled from Spain.
This year Tisha B'Av falls on the 29th of July. You can learn more about this holiday in: What Is Tisha B'Av?
Image: Destruction of Jerusalem by the Romans / Artist Unknown