Leviticus 16:23

"And Aaron shall come into the tent of meeting, and shall put off the linen garments, which he put on when he went into the holy place, and shall leave them there: and he shall bathe his flesh in water in a holy place, and put on his garments, and come forth, and offer his burnt-offering and the burnt-offering of the people, and make atonement for himself, and for the people. And the fat of the sin-offering shall he burn upon the altar. And he that letteth go the goat for Azazel shall wash his clothes, and bathe his flesh in water, and afterward he shall come into the camp. And the bullock of the sin-offering, and the goat of the sin-offering, whose blood was brought in to make atonement in the holy place, shall be carried forth without the camp; and they shall burn in the fire their skins, and their flesh, and their dung. And he that burneth them shall wash his clothes, and bathe his flesh in water, and afterward he shall come into the camp."

The "mopping up" activities after the high ceremonies of the day ended are in view here. The orders were for Aaron to go ahead and complete the usual ritual for the sin-offerings, already slain that their blood might be used in the atonement ritual, and that the carcasses should be carried outside the camp and burned. That the Atonement services were over is indicated by the fact that Aaron bathed himself and changed to the formal regalia of his office. Other procedures in the final activities included the ceremonial washing and changing garments of the men who carried out the burning of the carcasses, and of the person charged with loosing the goat in a distant wilderness.