Exodus 29:14

But the flesh of the bullock, and his skin, and his dung
The several parts and members of him, head, legs, feet and the skin taken off of him, and the dung that comes from him. Aben Ezra observes, that the flesh comprehends the head and the pieces, and may be interpreted in a way of conjecture, that he washed it, and afterwards burnt it; all representing a whole Christ under all his painful sufferings, and the shame and reproach he underwent in them:

shalt thou burn with fire without the camp;
so Christ, the antitype, suffered without the gates of Jerusalem a most painful and shameful death, despised and reproached by men, and the wrath of God like fire poured out upon him: the apostle seems to refer to this, ( Hebrews 13:11 Hebrews 13:12 ) ,

it is a sin offering;
in order to make atonement for the sins of Aaron and his sons; for the law made men priests that had infirmity, and needed offerings and sacrifices for their own sins, which shows the imperfection of the Aaronic priesthood.