Tisha B'Av (help·info) (Hebrew: תשעה באב‎ or ט׳ באב, "the Ninth of Av,") is an annual fast day in Judaism, named for the ninth day (Tisha) of the month of Av in the Hebrew calendar. The fast commemorates the destruction of both the First Temple and Second Temple in Jerusalem, which occurred about 655 years apart, but on the same Hebrew calendar date.^[1] Although primarily meant to commemorate the destruction of the Temples, it is also considered appropriate to commemorate other Jewish tragedies that occurred on this day, most notably the expulsion of the Jews from Spain in 1492.^[2] Accordingly, the day has been called the "saddest day in Jewish history".^[3]

Tisha B'Av falls in July or August in the western calendar. When the ninth of Av falls on Sabbath (Saturday), the observance is deferred to Sunday the tenth of Av. While the day recalls general tragedies which have befallen the Jewish people over the ages, the day focuses on commemoration of five events: the destruction of the two ancient Temples in Jerusalem, the sin of ten of the twelve scouts sent by Moses who spoke disparagingly about the Promised Land, the razing of Jerusalem following the siege of Jerusalem in 70 CE, and the failure of the Bar Kokhba revolt against the Roman Empire.