Midrasz do Liczb 3:3

4) (Vayikra 1:5) "and the sons of Aaron, the Cohanim, shall present (vehikrivu) the blood": I might think that this refers to z'rikah (dashing the blood on the altar). But z'rikah is already mentioned (following). How, then, am I to understand "vehikrivu"? As referring to the receiving of the blood — that it be done only by a Cohein kasher, and with a ministering vessel. R. Akiva said: Whence is it derived that the receiving of the blood be done only by a Cohein kasher? Kihun (priesthood) is mentioned here ("the sons of Aaron, the Cohanim"), and it is mentioned elsewhere [(Bamidbar 3:3): "These are the names of the sons of Aaron, whom he invested lechahein"]. Just as the kihun there is with a Cohein kasher and ministering vessels, so, the kihun here (in respect to the receiving of the blood).

33) (Vayikra 8:30): "And Moses took of the oil of anointment and of the blood which was upon the altar, and he sprinkled it upon Aaron, upon his garments, and upon his sons, and upon the garments of his sons with him. And he sanctified Aaron, his garments, and his sons, and the garments of his sons with him.": The three "bloods" mentioned in this section (the bullock of the sin-offering, the ram of the burnt-offering, and the ram of the miluim) are not alike. The first requires six applications; the second, two; and the third, thirteen. The first (the bullock of the sin-offering) requires sprinkling, application roundabout (on the four corners of the altar), purification (chitui, by application of the blood on the roof of the altar, viz. Shemoth 29:36) and spilling (yetzikah, of the blood at the base of the altar). The second (the ram of the burnt-offering) requires sprinkling and application roundabout. The third (the ram of the miluim) requires six "thumb" applications: three on Aaron (on the thumb of his hand, the big toe of his foot, and the tnuch of his ear), and three (respectively) on (each of) his sons. Others say: nine ("thumb" applications): three on Aaron and six on his sons. Others say: fifteen: three on Aaron and twelve on his four sons, viz. (Bamidbar 3:3): "These are the names of the sons of Aaron, the anointed Cohanim, whom he invested to minister." And it required (one) sprinkling on the altar (in sum, thirteen applications: six "thumb" applications, one altar sprinkling, and six sprinklings on Aaron and on his sons).