Yevamot (the plural of the word used to refer to one’s childless brother’s widow) is the first tractate in Seder Nashim (“Order of Women,” which addresses family law). Its sixteen chapters discuss yibum, the Torah-mandated marriage of a widow to the brother of her childless husband as well as chalitzah, the alternative rite discharging that obligation, in which the widow takes off the shoe of her husband’s brother and spits on the floor.