Yoma 14A

לומר שאינו עובד כל היום, גזירה שמא יאכל. אמר ליה רב אדא בר אהבה לרבא: ומי גזר רבי יהודה שמא יאכל? והתנן, רבי יהודה אומר: אף אשה אחרת מתקינין לו, שמא תמות אשתו. ואי מייתא אשתו עביד עבודה, ולא גזר רבי יהודה שמא יאכל! אמר ליה: הכי השתא?! התם, כיון דיום הכפורים הוא, דכולי עלמא לא קא אכלי, הוא נמי לא אתי למיכל, הכא, דכולי עלמא אכלי ⁠— הוא נמי אתי למיכל.

R' Yehuda means to say that the High Priest does not serve for the entire day even though the Torah allows him to do so, due to a rabbinic decree lest he forget that he is an acute mourner and eat consecrated food forbidden to him. Rav Adda bar Ahava said to Rava: And did R' Yehuda issue a decree lest he eat? But didn’t we learn in the Mishnah that R' Yehuda says: The rabbis would even designate another wife for him lest his wife die? And if his wife dies, he nevertheless performs the Temple service, and R' Yehuda did not issue a decree lest he eat. That contradicts the other statement by R' Yehuda that a High Priest may not serve for the entire day that he is an acute mourner. Rava said to him: How can these cases be compared? There, in the Mishnah, since it is Yom Kippur, when everyone does not eat, he too will not come to eat. However, here, during the rest of the year, when everyone eats, he too will come to eat. Therefore, a decree was issued.

וכי האי גוונא מי חיילא עליה אנינות? והא מיגרשא! נהי דאנינות לא חיילא עליה, אטרודי מי לא מיטריד?

The Talmud raises a question from a different perspective: And in a case like this, would the halakhic status of acute mourning take effect on him, considering that she is divorced? According to R' Yehuda, the High Priest must give his wife a provisional divorce in which case she is no longer his wife and if she dies he is no longer obligated to mourn her. The Talmud answers: Although the status of acute mourning does not take effect on him, is he not troubled over the death of his wife? Therefore, according to R' Yehuda, it is appropriate to prohibit his performance of the service on that day.