Halacha 1
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.
Halacha 2
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.
Halacha 3
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.
Halacha 4
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].
125. 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.
Halacha 6
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.
Halacha 7
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.
Halacha 8
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.
Women - Berachot 20b relates:
A woman's exemption from Kri'at Shema is obvious. It is a time-oriented commandment [i.e., the Shema must be recited at specific times and is thus classified as "time-oriented" (see Chapter 1, Halachot 9 to 13)], and women are exempt from all such commandments.
What might I have thought? That since [Kri'at Shema] contains the acceptance of the sovereignty of Heaven [even women would be called upon to recite it.
It [i.e., the Mishnah] teaches that this is not so and that women are indeed exempt from Kri'at Shema.
In terms of actual halachic ruling, the Shulchan Aruch, Orach Chayim 70:1 rules that although women have no obligation, even rabbinic, to recite the Shema, it is proper that they do so in order to accept upon themselves the yoke of the sovereignty of Heaven.
Women are also exempt from the blessings before Kri'at Shema, but are obligated to recite the blessings after it, because there is a mention of the Exodus from Egypt, which women are also obligated to remember and mention (Magen Avraham 70:1).
The Aruch Hashulchan (Orach Chayim 70:1) also mentions that women may recite all the blessings of Kri'at Shema and adds that the women of his area (Russia in the late nineteenth and early twentieth century) were accustomed to do so, and that they should be blessed for their meritorious actions.
The responsa, Yabia Omer (2:6), states that women of Sephardic origin are not accustomed to recite the blessings. However, Kaf HaChayim rules that they may.
slaves - This refers to Canaanite slaves who have been sold to a Jewish owner and are obligated by all the commandments that women are obligated to perform. A halachic comparison between the two is found in Chaggigah 4a and Kiddushin 23a.
The Jerusalem Talmud quotes a separate source for the exemption of slaves: "Hear O Israel, God our Lord, God is One" (Deuteronomy 6:4). He who has no master other than the Almighty [is obligated to recite the Shema], thus exempting the slave, who has another master.
Chaggigah 4a also derives the halachah in a similar fashion, albeit from a different verse.
and children - I.e., boys under the age of 13 years and one day. They are minors and exempt from all the Torah's commandments.
We should teach children to recite it at the proper time - The latter point represents a difference in opinion between Rashi and the Rambam. The Mishnah, Berachot 20a, states that children are free from the obligation to recite the Shema. Rashi states that they are entirely free of obligation even according to Rabbinic law because their parents may not be available at the specific times at which the Shema must be recited.
The Rambam and Rabbenu Tam differ and maintain that the mishnah is only referring to the obligations according to Torah law, but according to Rabbinic decree they are obligated. The Shulchan Aruch, Orach Chayim 70:2 rules in accordance with the Rambam and Rabbenu Tam.
with the blessings before and after it, in order to educate them regarding commandments - - According to Rashi (Berachot 48a) and the Ramban (Milchamot Hashem, Berachot 20b), there is no obligation incumbent on the child himself. Rather, the child's father is obligated to educate him. If he has no father, the obligation falls on his mother and on the local Rabbinic court (Terumat Hadeshen 99).
Tosafot (Berachot 48a) differs and explains that the Sages placed the obligation on the minor himself. Support for this premise can be derived from the Rambam's decision in Hilchot Berachot 5:15-16, which states that an adult who ate a small meal can fulfill his obligation to recite grace by listening to a child reciting those blessings (for both are obligated by virtue of Rabbinic decree). Though others object on the grounds that the child himself is not obligated in the mitzvah, the Rambam states that such a practice is acceptable.
One who is preoccupied and in an anxious state regarding a religious duty - Berachot 16b differentiates between a bridegroom, who is exempt because of his involvement in a mitzvah, and one whose ship is sinking in the sea. Though the latter individual is also anxious, he is obligated to recite the Shema, because his preoccupation is not with regard to a commandment.
is exempt from all commandments - This is based on the principle - העוסק במצוה פטור מן המצוה - One who is involved in one commandment is exempt from another (Sukkah 25a, Sotah 44b).
including Kri'at Shema. - I.e., even though it contains an acceptance of the yoke of the sovereignty of Heaven, he is still exempt.
The phrase, Deuteronomy 6:7, ובשבתך בביתך (and while you are sitting in your house) implies that the obligation is only incumbent on someone who is involved in his own personal affairs - "your house." Thus, it excludes one who is involved in the performance of a mitzvah (Berachot 11a and 16a).
Therefore, a bridegroom whose bride is a virgin is exempt from Kri'at Shema until he has consummated the marriage - The Mishnah, Berachot 16a, explains the derivation of the bridegroom's exemption. The phrase ובלכתך בדרך - "and as you go in your way" implies that the obligation to recite the Shema only applies to someone going on "your way," i.e., involved in his own personal affairs and not preoccupied with the fulfillment of a mitzvah as is a bridegroom. [In his commentary on that Mishnah, the Rambam mentions that the bridegroom is involved in the mitzvah of being fruitful and multiplying.]
Rashi explains that this concept could not be derived from the phrase בשבתך בביתך - "and while you are sitting in your house" because if there were only one verse, one would have thought that only one who is actually involved in the performance of a commandment is exempted. Thus, an additional phrase is necessary to exempt a bridegroom, who though not immediately involved in the performance of the mitzvah is in an anxious state, because of the possible problems inherent in the overall situation.
because he is distracted lest he not find her a virgin. - as explained above. Rabbenu Manoach writes in the name of the Ra'avad that the bridegroom is exempt from Kri'at Shema only if he is able to have relations with his wife. However, if she is menstruating or sick, he is obligated to recite the Shema.
Rabbenu Manoach also discusses the different views regarding the bridegroom's obligation to recite the Shema during the day if he does not engage in relations the first night. He concludes that he should be obligated since "the Jews are a holy people and the bridegroom will be able to divert his thoughts from his wife and concentrate on reciting the Shema."
And if he delays until Saturday night after the wedding - This is dependent on the Talmudic custom (Ketubot 2a), which relates that virgins would marry on Wednesday night.
and does not have relations with her, he is obligated to recite the Shema from that time onward, since - he has waited this long, we can assume that...
his mind has settled and he is familiar with her even though they have not consummated the marriage. - I.e., he is no longer nervous and distracted and can be expected to recite the Shema with the proper intention. In his commentary on the Mishnah, the Rambam mentions that by this time, his all-consuming desire to consummate the marriage has passed.
In this instance, the actual halachah does not reflect the Rambam's position. The Shulchan Aruch, Orach Chayim 70:3, mentions that bridegrooms were originally exempt from Kri'at Shema the first three days (i.e., days and nights) after the wedding. However, today, because of the general lack of intention that everyone has regarding Kri'at Shema, even the bridegroom is obligated to recite the Shema.
The Mishnah Berurah (70:14) adds that a bridegroom who does not recite the Shema appears haughty, because his actions appear to imply that he usually has a high level of intentions. The bridegroom is also obligated to recite the blessings before and after Kri'at Shema and to pray as usual (Magen Avraham; Mishnah Berurah). These positions are based on Tosafot in Berachot 17b.