Midrasch zu Schemot 29:9

4) (Vayikra 16:32) ("And the Cohein shall make atonement, who shall be anointed, and who shall be invested with the priesthood in place of his father; and he shall put on the linen garments, the holy garments.") "And the Cohein shall make atonement, who has been anointed": What is the intent of this? Because this entire section is written in respect to Aaron, I might think that it applies only to Aaron himself. Whence do I derive (for inclusion) a different Cohein? From "who shall be anointed." This tells me only of one anointed by the anointing oil. Whence do I derive (for inclusion a Cohein who wore) the many garments (i.e., the eight garments of the high-priest)? From "who shall be invested" (See Shemoth 29:9). Whence do I derive (for inclusion) a different Cohein who is appointed (to take his place if he becomes disqualified)? From "And the Cohein shall make atonement."

8) (Vayikra 10:9) "an everlasting statute throughout your generations": to include (for invalidation of the service after drinking): spillings (of blood), mixings (of wine or oil), wavings (of offerings), presentings (to the altar), (takings of) fistfuls (of meal-offerings), smokings of incense, "pinchings" (of bird offerings), receivings, and sprinklings (of blood). Whence is it derived that if a Cohein officiates after drinking his service is invalid? From (Vayikra 10:10): "So that you distinguish between the holy and the profane." And whence is derived (the invalidity of the service of) a Cohein who officiates lacking one of the priestly vestments or not having laved his hands and his feet? From the identity (gezeirah shavah) of "an everlasting statute" (here) — "for an everlasting statute" (Shemoth 29:9, in respect to the priestly vestments" — "an everlasting statute," (Shemoth 30:21, in respect to laving of hands and feet).