Since when may one recite the Shema in the evening? Since the time when the kohanim (priests) enter to eat their terumah (agricultural gifts). [It may be recited at any time since then] until the end of the first watch [of the night]; this is the view of Rabbi Eliezer. The Sages say: [The Shema may be recited] until midnight. Rabban Gamliel says: [It may be recited] until dawn breaks (lit. the column of dawn rises). "If so, why did the Sages say [that these precepts can be performed only] until midnight? To keep a person away from sinning."