Numbers 18:1

And the Lord said unto Aaron, for the fact of his priesthood was now practically unchallenged among the children of Israel, Thou and thy sons and thy father's house with thee, the entire family in all its descendants, shall bear the. iniquity of the Sanctuary, they were to consider themselves responsible for the removal of any defilement which might come upon the Tabernacle and its equipment while it was being used for purposes of worship: and thou and thy sons with thee shall bear the iniquity of your priesthood, whatever impurities and imperfections still clung to them in the work of their calling. It was for the removal of these sins as they resulted from the natural sinful condition of men that the animal atonement had been ordered by God, Leviticus 16:16.