Brachot 2 - Saying the Shema Prayer
Twice a day, evening and morning, one has to say that he will listen to God and love God. This is the "Shema" prayer, " Listen, Israel, God is our Lord, God is One. " Since the Torah continues, " when you lie down and when you get up ," we understand that this paragraph needs to be said twice.
However, the Shema is not said when one actually does to sleep or wakes up, but rather in the general time period when people lie down and when they get up. When is this? In the evening - when the Kohanim, who were impure, are returning from the mikveh to eat priestly portion (terumah), that is, at nightfall. That is when the time to say the Shema in the evening begins, but when does it end? Rabbi Eliezer said, "Until the end of the first watch, that is, the first part of the night." Rabbi Eliezer understands "when you lie down" as the time when people go to sleep. The Sages say, until midnight, and Rabban Gamliel says, until dawn. We can understand Rabban Gamliel, according to him, "when people lie down" means when people are asleep. But the opinion of the Sages will require clarification.
Why did the teacher not state simply, "nightfall," and instead talked about Kohanim coming home? - Because he wanted to teach an additional rule in passing, that the Kohanim can start eating their portion at night, after immersion. That is true even if they had a severe impurity, such as that of a zav , and still need to bring a sacrifice - that offering does not prevent them from eating their kohen's portion.
Art: Vincent Van Gogh - Four Peasants at a Meal