ר"ע אומר מישאל ואלצפן היו שהיו עוסקין בנדב ואביהוא ר' יצחק אומר אם נושאי ארונו של יוסף היו כבר היו יכולין ליטהר אם מישאל ואלצפן היו יכולין היו ליטהר
Rabbi Akiva says: They were Mishael and Elzaphan, who were engaged in carrying the bodies of Nadav and Avihu after they were burned in the Holy of Holies (see Leviticus 10:4). Rabbi Yitzḥak says: These identifications are inaccurate, because if they were the bearers of Joseph’s coffin, they could have already been purified. They were camped at Sinai sufficient time to become purified in time to sacrifice the Paschal lamb. And if they were Mishael and Elzaphan they could have already been purified, as the Tabernacle was erected on the first of Nisan, which was the eighth day of the inauguration, when the sons of Aaron were burned. More than seven days remained until the eve of Passover on the fourteenth of Nisan.
אלא עוסקין במת מצוה היו שחל שביעי שלהן להיות בערב פסח שנאמר (במדבר ט, ו) ולא יכלו לעשות הפסח ביום ההוא ביום ההוא אין יכולין לעשות הא למחר יכולין לעשות
Rather, they were unnamed people who were engaged in tending to a corpse whose burial is a mitzva, i.e., which has no one else available to bury it, and their seventh day of impurity occurred precisely on the eve of Passover, as it is stated: “And they could not observe the Pesaḥ on that day” (Numbers 9:6). The Gemara infers: On that day they could not observe it; on the next day they could observe it. Although they would be purified at nightfall and would then be eligible to partake of the Paschal lamb, at the time of the slaughter and the sprinkling of the blood they were not yet pure. They asked whether the Paschal lamb could be slaughtered on their behalf. Apparently, they were obligated to perform the mitzva of burial of the corpse although it prevented them from fulfilling the mitzva of sacrificing the Paschal lamb, which is a stringent mitzva. This is the source for the principle that one engaged in the performance of a mitzva is exempt from performing another mitzva.
צריכא דאי אשמעינן התם משום דלא מטא זמן חיובא דפסח אבל הכא דמטא זמן ק"ש אימא לא צריכא ואי אשמעי' הכא משום דליכא כרת אבל התם דאיכא כרת אימא לא צריכא
The Gemara answers: Both sources are necessary. As, if it had taught us there, in the case of impurity imparted by a corpse, the conclusion would have been that the exemption from sacrificing the Paschal lamb is due to the fact that the time of the obligation of the Pesaḥ had not yet arrived when they were obligated to bury the corpse, and therefore they proceeded to fulfill the mitzva that they encountered first. However, here, where the time to recite Shema had already arrived during the wedding, say no, that the groom is not exempt; therefore, it is necessary to teach that the groom is exempt. And if it had taught us here, with regard to Shema, the conclusion would have been that the exemption from Shema is due to the fact that it is not a stringent mitzva, as there is no karet administered to one who fails to fulfill it. However, there, with regard to the Paschal lamb, where there is karet administered to one who fails to observe the Pesaḥ, say that one is not exempt from performing it. Therefore, it is necessary to teach both cases.
גופא א"ר אבא בר זבדא אמר רב אבל חייב בכל מצות האמורות בתורה חוץ מתפילין שהרי נאמר בהן פאר מדאמר ליה רחמנא ליחזקאל (יחזקאל כד, יז) פארך חבוש עליך וגו' את הוא דמיחייבת אבל כ"ע פטירי
§ With regard to the matter itself, Rabbi Abba bar Zavda said that Rav said: A mourner is obligated in all the mitzvot mentioned in the Torah except for the mitzva to don phylacteries, from which a mourner is exempt, as the term splendor is stated with regard to phylacteries, and it is not proper for a mourner to adorn himself in this manner. This is derived from the fact that the Merciful One said to Ezekiel: “Sigh in silence; make no mourning for the dead, bind your splendor upon you, and put your shoes upon your feet” (Ezekiel 24:17). Ezekiel was commanded to refrain from mourning for his wife in the manner that others do. God said to Ezekiel: You are obligated to don phylacteries even while mourning; however, everyone else is exempt.
וה"מ ביום ראשון דכתיב (עמוס ח, י) ואחריתה כיום מר
The Gemara comments: This exemption applies only on the first day of mourning, as it is written: “And I will make it as the mourning for an only son, and the end thereof as a bitter day” (Amos 8:10). From this verse it is derived that the primary bitterness of a mourner lasts only one day.
ואמר רבי אבא בר זבדא אמר רב אבל חייב בסוכה פשיטא מהו דתימא הואיל וא"ר אבא בר זבדא אמר רב מצטער פטור מן הסוכה האי נמי מצטער הוא קמשמע לן ה"מ צערא דממילא אבל הכא איהו הוא דקא מצטער נפשיה איבעי ליה ליתובי דעתיה
On a similar note, Rabbi Abba bar Zavda said that Rav said: A mourner is obligated in the mitzva of sukka. The Gemara asks: That is obvious; why would he be exempt? The Gemara answers: Lest you say that since Rabbi Abba bar Zavda said that Rav said that one who is suffering due to his presence in the sukka is exempt from the mitzva of sukka, one could have said that this mourner too is one who is suffering and should be exempt as well. Therefore, he teaches us that the mourner is obligated in the mitzva of sukka. These cases are not similar, since this exemption from sukka applies only with regard to suffering that is caused by the sukka itself, e.g., when one is cold or hot or when the roofing has a foul odor. However, here, in the case of a mourner, where he is causing himself to suffer unrelated to his presence in the sukka, he is required to settle himself and fulfill the mitzva.
וא"ר אבא בר זבדא אמר רב חתן והשושבינין וכל בני החופה פטורין מן הסוכה כל שבעה מ"ט משום דבעו למיחדי וליכלו בסוכה וליחדו בסוכה אין שמחה אלא בחופה וליכלו בסוכה וליחדו בחופה אין שמחה אלא במקום סעודה
§ And Rabbi Abba bar Zavda said that Rav said: The groom and the groomsmen and all members of the wedding party who participate in the wedding celebration are exempt from the mitzva of sukka for all seven days of the wedding celebration. The Gemara asks: What is the reason that they are exempt? It is because they wish to rejoice. The Gemara asks: And let them eat in the sukka and rejoice in the sukka. The Gemara answers: The celebration of a wedding is only in the wedding home where the newlyweds reside after the marriage ceremony. The Gemara asks: So let them eat in the sukka like everyone else and rejoice in the wedding home. The Gemara answers: There is joy only in the place where there is a meal. Therefore, since the celebration must be in the home of the newlyweds, the meal must also be there.
וליעבדו חופה בסוכה אביי אמר משום ייחוד ורבא אמר משום צער חתן מאי בינייהו איכא בינייהו דשכיחי אינשי דנפקי ועיילי להתם למאן דאמר משום ייחוד ליכא למאן דאמר משום צער חתן איכא
The Gemara asks: And let them establish the wedding home in the sukka. Abaye said: This may not be done due to the prohibition against seclusion of the bride with a man other than her husband. As the sukka was often established on a rooftop, if the groom went downstairs at any point, the bride could find herself alone in the sukka with a man. And Rava said: The reason is due to the suffering of the groom. Since the sukka is not enclosed on all sides, he will be unable to enjoy privacy with his bride. The Gemara asks: What is the practical difference between them? The Gemara answers: The practical difference between them is in a case where people regularly enter and leave the sukka. According to the one who said that the reason is due to the prohibition against being alone together, there is no room for concern in that case. However, according to the one who said that the reason is due to the suffering of the groom, there is room for concern in that case as well.
א"ר זירא אנא אכלי בסוכה וחדי בחופה וכ"ש דחדי ליבאי דקא עבידנא תרתי
Rabbi Zeira said: I married on the eve of the festival of Sukkot and I ate in the sukka and rejoiced in the wedding home, and all the more so my heart rejoiced as I fulfilled two mitzvot: The mitzva of marriage and the accompanying celebration, and the mitzva of sukka. Nevertheless, he did not require others to do the same.
ת"ר חתן והשושבינין וכל בני חופה פטורין מן התפלה ומן התפילין וחייבין בק"ש
The Sages taught: The groom and the groomsmen and all the members of the wedding party are exempt from the mitzva of prayer and from the mitzva of phylacteries because they are unable to muster the requisite intent due to the excess of joy and levity; but they are obligated in the mitzva of reciting Shema.