Commentaire sur Le Lévitique 7:33

‎'וגו‎‎‎‎‎‎‎‏‎ השלמים ‎ ‏‏‎דם‎ ‎את ‎‎המקריב‎ [HE AMONG THE SONS OF AARON] THAT OFFERETH THE BLOOD OF THE PEACE-OFFERINGS [AND THE FAT SHALL HAVE THE SHOULDER OF THE RIGHT SIDE FOR HIS PART] — “He that offereth the blood” means: he who is fitted to perform the sprinkling of it and to burn the fat portions, — thus excluding a priest who was unclean at the time when the blood was sprinkled, or the fat portions were burnt — that he does not share in the flesh (Sifra, Tzav, Chapter 16 8; Zevachim 98b).

Or at the time of burning. Although above, regarding the sin-offering, Rashi writes only (6:19): “Excluding the one who is impure at the time of sprinkling the blood,” this is because Scripture writes here: “And the fat,” which implies that he needs to be pure at the time of burning the fat [as well] (Gur Aryeh).