Rashi on Exodus 29:29/רש"י על שמות כ״ט:כ״ט

1לבניו אחריו [SHALL BE] FOR HIS SONS AFTER HIM — for him who comes after him in this high office.

2למשחה means to be raised to dignity by means of them. For sometimes the word משח is used in the sense of “dignity”, as in (Numbers 18:8), “to thee I have given them as a dignity (למשחה)”, and (I Chronicles 16:22) “Touch ye not my nobles (משיחי)” (cf. Rashi on Exodus 30:29).

3ולמלא בם את ידם AND TO BE CONSECRATED BY THEM — through these garments he is to be invested with the high-priesthood (cf. Rashi on Yoma 73a).