申命記 16:3 哈拉卡：Mishneh Torah, Reading the Shema, Mishneh Torah, Leavened and Unleavened Bread & Abudarham

Although the precept to wear fringes is not incumbent at night, still the section concerning this precept is recited at night, because it mentions the departure from Egypt, which it is a duty to recall by day and at night, as it is said, "that thou mayest remember the day of thy going forth from the land of Egypt all the days of thy life" (Deuteronomy 16:3). The reading of these three sections in this order is termed "The reading of the Shema."

It is forbidden to eat chamets on the fourteenth from midday - which is the beginning of the seventh hour of the day (if the day is divided into twelve hours) - and onward. And anyone that eats [it] at that time is lashed by Torah writ, as it is stated (Deuteronomy 16:3), "You shall not eat chamets upon it" - meaning to say, upon the Passover sacrifice. Thus did they learn the explanation of this thing from the oral tradition: "You shall not eat chamets" from the time that is fit for the sacrifice of the Passover sacrifice, which is in "the afternoon" (Exodus 12:6) - and that is half the day.

He who has been bereaved of a relative for whom he has to keep the period of mourning is exempted from reading the Shema till he has buried the body, as his mind is not free for reading it. A watcher, even if the body is not that of a relative, is exempt from reading the Shema. When there are two watchers, one watches while the other withdraws to another room and reads it. Then he returns and watches while his companion withdraws and reads it. So too, one who is engaged in digging a grave for the interment of a human body is exempt, for the time being, from reading the Shema.