I have given them — Not only the charge, but the use of them for thyself and family. By reason of the anointing — That is, because thou art priest, and art to devote thyself wholly to my service.
Related Commentaries of Numbers 18:8
Numbers 18:8
8 And the LORD spake unto Aaron, Behold, I also have given thee the charge of mine heave offerings of all the hallowed things of the children of Israel; unto thee have I given them by reason of the anointing, and to thy sons, by an ordinance for ever.