Nazir 49A

ולרבי עקיבא, מכדי לא שנא כהן גדול לחודיה ולא שנא כהן גדול והוא נזיר, נפקא מ״לאחיו״, ״לאביו ולאמו״ למה לי?

The Talmud asks: And according to the derivation of R' Akiva, now consider, it is no different whether the individual was a High Priest alone, and it is no different if he was a High Priest who was also a nazirite; the halakha that he must become impure to bury a met mitzva is derived from the phrase “for his brother,” stated with regard to a nazirite (Numbers 6:7). But if so, why do I need the expression “for his father, or for his mother” (Numbers 6:7)? The general prohibition against contracting impurity from any corpse should suffice.

צריכי: דאי כתב ״אביו״, הוה אמינא: היינו טעמא דלא מיטמא ליה ⁠— משום דחזקה בעלמא הוא. אבל אמו דידעין דילידתיה ⁠— ליטמא לה.

The Talmud answers: Both are necessary, as had the verse written only “for his father,” I would say that this is the reason that a nazirite may not become impure for his father: Because it is merely a presumption that he is his father, as one cannot be absolutely sure of the identity of one’s father. However, with regard to his mother, whom we know gave birth to him, perhaps let him become impure to bury her. The verse therefore states: “His mother.”

ואי כתב רחמנא ״אמו״, הוה אמינא: אמו לא ליטמא לה, דלאו אזיל זרעה בתרה. אבל אביו, כיון דאמר מר ״למשפחותם לבית אבותם״, אימא ליטמא ליה ⁠— קא משמע לן.

And conversely, had God written only “for his mother,” I would say that it is solely to bury his mother that he may not become impure, as her seed does not follow her, i.e., a man’s lineage is determined by his father, not his mother. However, with regard to his father, since the Master said with regard to the verse “by their families, by their fathers’ house” (Numbers 1:2) that one’s family ancestry follows his father, you might say: Let him become impure to bury him. The verse therefore teaches us that a nazirite may not become impure to bury his father either.