Sanhedrin 35B

ושמע שמת לו מת, יכול יטמא? אמרת: ״לא יטמא״.

and he heard that a relative of his died, one might have thought that he should return and become ritually impure with the impurity imparted by a corpse to bury his relative. You said: “He should not make himself impure”; the death of his relative will not override so significant a mitzva from the Torah.

יכול, כשם שאינו מטמא לאחותו כך אינו מטמא למת מצוה? תלמוד לומר: ״ולאחתו״. לאחותו הוא דאינו מטמא, אבל מטמא למת מצוה.

One might have thought: Just as he may not become impure to bury his sister, so he may not become impure to bury a met mitzva. Therefore, the verse states specifically: “Or for his sister”; teaching that he may not become impure only to bury his sister, as others can attend to her burial, but he may become impure to bury a met mitzva.

שבת שנידחת מפני עבודה, אינו דין שתהא קבורת מת מצוה דוחה אותה?

Having cited the baraita proving that the burial of a met mitzva overrides the Temple service, Reish Lakish continues his suggestion: With regard to Shabbat, which is overridden due to the Temple service, is it not logical that the burial of a met mitzva overrides it?

אמר ליה: רציחה תוכיח, שדוחה את העבודה ואינה דוחה את השבת.

R' Yoḥanan said to him: The halakha of murder, i.e., the obligation to kill one found liable to receive court-imposed capital punishment, proves that this is not the case, as it overrides the Temple service, e.g., if the only priest present is liable to receive court-imposed capital punishment, he is taken to be killed despite this resulting in the negation of the Temple service, but it does not override Shabbat.

רציחה גופה תדחה את השבת מקל וחומר: מה עבודה שדוחה את השבת, רציחה דוחה אותה, שנאמר ״מעם מזבחי תקחנו למות״; שבת שנידחת מפני עבודה, אינו דין שתהא רציחה דוחה אותה?

The Talmud asks: Murder itself should override Shabbat based on this a fortiori inference: Just as with regard to the Temple service, which overrides Shabbat, nevertheless murder overrides it, and the source for this is as it is stated: “And if a man come presumptuously upon his neighbor, to slay him with guile; you should take him from My altar, that he may die” (Exodus 21:14); then with regard to Shabbat, which is overridden due to the Temple service, is it not logical that murder should override it?