Charles Ellicott Commentary Numbers 18:1

"And Jehovah said unto Aaron, Thou and thy sons and thy fathers` house with thee shall bear the iniquity of the sanctuary; and thou and thy sons with thee shall bear the iniquity of your priesthood." — Numbers 18:1 (ASV)

Shall bear the iniquity of the sanctuary ... — It must be remembered that the iniquity of the sanctuary, and the iniquity of the priesthood, extended not only to the defilement of the sanctuary by the transgressions of priests and people (Leviticus 16:11; Leviticus 16:15–16), but also to its defilement by the imperfections connected with the services of the priests and the offerings of the people (Exodus 28:38).