Tisha B'Av is the deepest fast in the calendar and the one most likely to be skipped. It commemorates the destruction of both Temples, and tradition attaches to the same date the fall of Betar at the end of the Bar Kochba revolt, the expulsion of the Jews from Spain in 1492, and a list that grows. The observance is full mourning: fasting from sunset to nightfall, no leather shoes, no washing beyond the necessary, no marital relations, no greeting one another, sitting on the floor or on low stools until midday, and a prohibition on studying Torah except for the sorrowful parts. Lamentations is chanted by candlelight in a dirge melody used nowhere else, followed by kinot, elegies accumulated over a thousand years, including several written after the Crusades and some written after the Shoah. Three weeks of increasing restriction precede it. The Israeli argument around it is real: religious Zionists debate whether a day of mourning for the loss of Jerusalem still makes sense with Jews governing Jerusalem, and secular Israelis resent that the law closes restaurants on a fast day they do not keep.