Berakhot 3:43

['One whose deceased relative is laid out unburied before him is exempt from the recitation of Shema, from the Amida prayer, and from the mitzva to don phylacteries, as well as all positive mitzvot mentioned in the Torah, until the deceased has been buried. With regard to the pallbearers and their replacements and the replacements of their replacements, those located before the bier who have not yet carried the deceased and those located after the bier. Those who are needed to carry the bier are exempt from reciting Shema; while those who are not needed to carry the bier, are obligated to recite Shema. However, both these and those are exempt from reciting the Amida prayer, since they are preoccupied and are unable to focus and pray with the appropriate intent.', 'After they buried the deceased and returned, if they have sufficient time to begin to recite Shema and conclude before they arrive at the row, formed by those who attended the burial, through which the bereaved family will pass in order to receive consolation, they should begin. If they do not have sufficient time to conclude reciting the entire Shema, then they should not begin. And those standing in the row, those in the interior row, directly before whom the mourners will pass and who will console them, are exempt from reciting Shema, while those in the exterior row, who stand there only to show their respect, are obligated to recite Shema.', 'Women, slaves and minors are exempt from the recitation of Shema and from phylacteries, but are obligated in prayer, mezuza and Grace after Meals.', 'Ezra the Scribe decreed that one who is ritually impure because of a seminal emission may not engage in matters of Torah until he has immersed in a ritual bath and purified himself. This halakha was accepted over the course of many generations; however, many disputes arose with regard to the Torah matters to which it applies. Regarding this, the mishna says: If the time for the recitation of Shema arrived and one is impure due to a seminal emission, he may contemplate Shema in his heart, but neither recites the blessings preceding Shema, nor the blessings following it. Over food which, after partaking, one is obligated by Torah law to recite a blessing, one recites a blessing afterward, but one does not recite a blessing beforehand, because the blessing recited prior to eating is a requirement by rabbinic law. And in all of these instances Rabbi Yehuda says: He recites a blessing beforehand and thereafter in both the case of Shema and in the case of food. ', 'This mishna contains various statements with regard to individuals with different types of ritual impurity as well as the need to distance oneself from filth and impurity. One who was standing in prayer and he recalled that he experienced a seminal emission, and according to this opinion he is prohibited from praying, should not interrupt his prayer, rather he should abridge each individual blessing. They stated a general principle: One who descended to immerse himself, if he is able to ascend, cover himself with a garment, and recite the morning Shema before sunrise, he should ascend, cover himself, and recite Shema, and if not, he should cover himself in the water and recite Shema there. He may not, however, cover himself in either foul water, or water in which flax was soaked, until he pours other water into it. And in general, how far must one distance himself from urine and feces in order to recite Shema? At least four cubits.', 'Continuing the earlier discussion of the halakhot of immersion for Torah study and prayer for one who experienced a seminal emission, the mishna discusses a case where individuals who were already impure with a severe form of ritual impurity are exposed to the impurity of a seminal emission as well. They are required to immerse themselves and purify themselves of the impurity of the seminal emission even though they remain impure due to the more severe impurity. Consequently, even a zav, whose impurity lasts at least seven days, who experienced a seminal emission, for which, were he not a zav, he would be impure for only one day; a menstruating woman who discharged semen, despite the fact that she is already impure with a severe impurity unaffected by her immersion; and a woman who engaged in conjugal relations with her husband and later saw menstrual blood, all require immersion. And Rabbi Yehuda exempts them from immersion.']