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. 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. Accordingly, the day has been called the "saddest day in Jewish history".

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.

Zev Leff, Rav of moshav Matityahu, Mateh Binyamin, Israel, is an American-born Orthodox Jewish rabbi and a widely-popular Torah educator who teaches and lectures regularly at English-speaking yeshivot, girls' schools, community centers, synagogue functions, and other events in Israel, as well as in England, South Africa and the United States. Known for his wit, humor and analytical brilliance, Rabbi Leff's taped lectures on Torah and Jewish themes are distributed worldwide. He is also the author of a book on the weekly Torah portion and a prolific columnist for English-language newspapers and magazines.

Born in the Bronx, New York to non-observant Jewish parents, Rabbi Leff attended a local Hebrew school. When his family moved to the Greater Miami area, he decided to increase his religious observance and enrolled at the Hebrew Academy of Greater Miami. Since his learning skills were not up to par with other boys his age (fifth grade), he was placed in a third-grade class. Within two years he had caught up to his grade, and also made the decision to become Shomer Shabbat.