Commentaire sur Le Lévitique 6:15

המשיח תחתיו מבניו is the same as המשיח מבניו תחתיו THE PRIEST THAT IS ANOINTED FROM AMONGST HIS SONS IN HIS STEAD.

והכהן המשיח תחתיו מבניו, and one of his sons, the priest who will be anointed in his stead, etc. The sages in Menachot 51 explain that this verse teaches that if a High Priest has died and no successor has as yet been appointed, that one of his sons must offer the daily meal-offering which is mandatory for the High Priest. They derive this הלכה from the words מבניו תחתיו, "one of his sons in his stead." The same sages use the letter ם in the word מבניו for a different exegetical purpose. The Talmud on that folio quotes a Baraitha according to which the word בניו means that the High Priest's sons enjoy the status of ordinary priests; to the query that may be the Torah intended them to have the status of High Priests (pl)? The sages point to the words והכהן המשיח תחתיו מבניו as proof that only one of the sons may be anointed as High Priest in place of their father. It seems clear that this conclusion is derived from the word מבניו, i.e. from amongst his sons, not all his sons.

The one anointed of his sons in his stead. Rashi explains by changing [the order of] the verse because we could have explained המשיח תחתיו — the anointing shall be in his stead. Or, we could have explained it as: “the anointed in his stead of his sons, shall bring the offering,” i.e., the son should bring the offering. Therefore, Rashi explains by changing the verse so that “in his stead” will be connected to “of his sons” and not with “the one anointed”; “in his stead” connotes one person in succession to another (Minchas Yehudah). See Kitzur Mizrachi, Mahara’n, Gur Areyeh, and Divrei Dovid — each one has a unique approach in this. Meaning: According to the verse’s order it would seem that the anointed one in his stead who is one of his sons shall offer this meal-offering, to exclude an anointed one who is not one of his sons — that he should not offer. This cannot be. But now [that Rashi reverses it] it means the anointed of his sons in his stead shall offer it [always], to exclude any of his sons who is not anointed shall not offer it [always] (Kitzur Mizrachi).