Read: Leviticus 10:11-20
Aaron replied to Moses, Today they sacrificed their sin offering and their burnt offering before the Lord, but such things as this have happened to me. Would the Lord have been pleased if I had eaten the sin offering today? When Moses heard this, he was satisfied. Lev 10:19-20
Do you see the problem here? There were two kinds of sin offering, as explained in the law of the sin offering in Chapter 6. In one the blood was to be carried into the inner sanctuary, into the holy place, and there it was to be sprinkled on the horns of the golden altar of fragrant incense. That was required as a picture of the depravity of man’s evil. And because of that depravity no part of the animal was to be eaten but it was all to be taken outside the camp and burned.
But there was another kind of sin offering in which the blood was sprinkled on the horns of the brazen altar in the outer court. There the flesh of the animal was to be eaten by the priests as a picture of their understanding of the nature of their evil and as a token of their acceptance of the forgiveness of God.