Mishneh Torah (Rambam) משנה תורה

Women, slaves and children are exempt from Kri'at Shema. We should teach children to recite it at the proper time with the blessings before and after it, in order to educate them regarding the commandments. One who is preoccupied and in an anxious state regarding a religious duty is exempt from all commandments, including Kri'at Shema. Therefore, a bridegroom whose bride is a virgin is exempt from Kri'at Shema until he has consummated the marriage, because he is distracted lest he not find her a virgin. However, if he delays until Saturday night after the wedding and does not have relations with her, he is obligated to recite the Shema from that time onward, since his mind has settled and he is familiar with her even though they have not consummated the marriage.

However, one who marries a woman who is not a virgin is obligated to recite the Shema, because even though he, too, is involved in the performance of a mitzvah, it is not so distracting. The same principle applies to similar cases.

One who is bereaved of a relative for whom he is obligated to mourn is exempt from Kri'at Shema until he has buried him, because his attention is distracted from reciting [the Shema]. A person who is watching a body is also exempt, even if it is not the body of a relative. When there are two watchers, one should continue watching while the other withdraws and recites the Shema. [When the latter] returns, the other should depart and recite [the Shema]. A gravedigger is also exempt from Kri'at Shema.

A body should not be taken out for burial close to the time for reciting the Shema, unless the deceased was a great man. If they do begin to remove the deceased and the time for reciting the Shema arrives while they are accompanying the body, anyone required to [carry] the coffin - e.g., the bearers of the coffins and their replacements and those who, in turn, relieve the replacements - whether they are before the coffin or after it, are exempt [from Kri'at Shema]. The rest of those accompanying the body who are not required to [carry] the coffin are obligated [to recite the Shema].

Should they be involved in eulogies when the time for Kri'at Shema arrives, if they are in the presence of the deceased they should withdraw singly and recite, and then return to the eulogy. If the deceased is not present, all the people should recite the Shema except the mourner, who remains silent, because he is not obligated to recite the Shema until he buries his relative.

After the burial, the mourners return to receive condolences and the people follow them from the gravesite to the place where they form a line to receive condolences. If the people are able to start and finish even one verse [of Kri'at Shema] before they arrive at the line, they should do so. If not, they should not start until they have consoled the mourners. After they have taken their leave they should commence reciting. Those standing in the inner line - i.e., they can see the faces of the mourners - are exempt from Kri'at Shema. Those at the outside, since they cannot see the mourner, are obligated to recite the Shema where they are.

Anyone who has an exemption from Kri'at Shema, but nevertheless desires to be strict with himself and recite, may do so. This is conditional upon the fact that his mind is not distracted. However, if this exempted person is in a confused state, he is not permitted to recite [the Shema] until he composes himself.

All those ritually impure are obligated to read the Shema and recite the blessings before and after it in their impure state. This applies even when it is possible for them to purify themselves that day - e.g., one who has touched [the carcass of] a שרץ (crawling animal), a menstrual woman, a זבה, or the couch on which these people have laid, and the like. Ezra and his colleagues decreed that a man who had a seminal emission was forbidden to read the words of the Torah. Thus, they separated him from the other ritually impure until he immersed himself in a mikveh. This ordinance was not universally accepted among the Jewish people. Most were unable to observe it and it was therefore negated. The Jewish people accepted the custom of reading the Torah and reciting the Shema even after a seminal emission, because the words of Torah cannot contract ritual impurity. Rather, they stand in their state of purity forever, as [Jeremiah 23:29] states: "Are not my words like fire, declares the Lord." Just as fire is incapable of becoming ritually impure, so, too, the words of Torah are never defiled.