John Wesley on Numbers 18:1

Shall bear the iniquity of the sanctuary - Shall suffer the punishment of all the usurpations, or pollutions of the sanctuary, or the holy things, by the Levites, or any of the people, because you have power from me to keep them all within their bounds. Thus the people are in good measure secured against their fears. Also they are informed that Aaron's high dignity was attended with great burdens, having not only his own, but the people's sins to answer for; and therefore they had no such reason to envy him, if the benefits and dangers were equally considered. The iniquity of your priesthood - That is, Of all the errors committed by yourselves, or by you permitted in others in things, belonging to your priesthood.