Albert Barnes 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)

The iniquity of the sanctuary - i.e., the guilt of the offences which an erring people would be continually committing against the majesty of God, when brought into contact, through the ordinances, with the manifestations of His presence. Compare the marginal reference.

The iniquity of your priesthood - As the priests themselves were but men, they were strengthened to bear the iniquity of their own unintentional offences, by being entrusted with the ceremonial means of taking it away . The word “bear” has, in the Old Testament, this double sense of “enduring” and “removing”; but in the person of Christ, who atoned by His own endurance, the two are, in effect, one.