Leviticus 8:15

And he slew it. — Better, and he killed it, as it is rendered in the Authorised Version, in Leviticus 8:19. In ordinary cases the offerer himself slaughtered the victim (see Leviticus 1:5), but in the case before us Moses performed this act in accordance with the command in Exodus 29:11.

And Moses took the blood. — That is, having caught the blood in the bowl, he threw it upon the four corners of the altar, as described in Leviticus 1:5 — not, however, on the horns of the altar of incense, or in the tabernacle, as in the case of the sin offering for the high priest and for the nation. (See Leviticus 4:7; Leviticus 4:16.)

And purified the altar... and sanctified it. — Like the priest, the altar was consecrated to the service of God by the anointing oil (see Leviticus 8:11), and hence, like the priest, the altar is also purified by the expiatory sacrifice from its defilements.