From what time may one recite the Shema in the evening? From the time that the priests enter [their houses] in order to eat their terumah until the end of the first watch, the words of Rabbi Eliezer. The sages say: until midnight. Rabban Gamaliel says: until dawn. Once it happened that his sons came home [late] from a wedding feast and they said to him: we have not yet recited the [evening] Shema. He said to them: if it is not yet dawn you are still obligated to recite. And not in respect to this alone did they so decide, but wherever the sages say “until midnight,” the mitzvah may be performed until dawn. The burning of the fat and the pieces may be performed till dawn. Similarly, all [the offerings] that are to be eaten within one day may be eaten till dawn. Why then did the sages say “until midnight”? In order to keep a man far from transgression.

From what time may one recite the Shema in the morning? From the time that one can distinguish between blue and white. Rabbi Eliezer says: between blue and green. And he must finish it by sunrise. Rabbi Joshua says: until the third hour of the day, for such is the custom of the children of kings, to rise at the third hour. If one recites the Shema later he loses nothing, like one who reads in the Torah.

Bet Shammai say: in the evening every man should recline and recite [the Shema], and in the morning he should stand, as it says, “And when you lie down and when you get up” (Deuteronomy 6:7). Bet Hillel say that every man should recite in his own way, as it says, “And when you walk by the way” (ibid). Why then is it said, “And when you lies down and when you get up?” At the time when people lie down and at the time when people rise up. Rabbi Tarfon said: I was once walking by the way and I reclined to recite the Shema according to the words of Bet Shammai, and I incurred danger from robbers. They said to him: you deserved to come to harm, because you acted against the words of Bet Hillel.

In the morning he recites two blessings before it and one after it; in the evening two before it and two after it, one long and one short. Where they [the sages] said that a long one should be said, he may not say a short one; where they said a short one he may not say a long one [Where they said] to conclude [with a blessing] he is not permitted to not conclude; where they said to not conclude [with a blessing], he may not conclude.