Tisha B'Av - Fast of 9th Av Aside from Yom Kippur, Tisha B'Av is the most important fast of the year. It commemorates: The destruction of both the First and the Second Temples (586 BCE and 70 CE) The fall of Bethar in the Bar Kochba rebellion (135 CE.). This final disaster marked the end of all Jewish aspirations for freedom from Rome. In later centuries other sad occurrences were associated with this day, one of the most significant being the expulsion of the Jews from Spain in 1492. Observance. The severity of the 9th Av matches the Day of Atonement insofar as both fast days commence on the previous evening. The synagogue presents a gloomy appearance, for the lights are dimmed, the curtain is removed from the Ark, and the worshippers sit on low stools or on the floor. Prayers of lamentation - kinnot - are recited and Echah, The Book of Lamentations, is read. The tallit and tephillin (phylacteries) which are considered religious adornments are not worn during the morning service. Instead, they are worn in the afternoon service. Only essential work is permitted.