Jamieson, Fausset and Brown on Leviticus 4:11

11. the skin of the bullock, and all his flesh--In ordinary circumstances, these were perquisites of the priests. But in the expiation necessary for a sin of the high priest, after the fat of the sacrifice was offered on the altar, the carcass was carried without the camp [Le 4:12], in order that the total combustion of it in the place of ashes might the more strikingly indicate the enormity of the transgression, and the horror with which he regarded it (compare He 13:12, 13).