Numbers 3:10

And thou shalt appoint Aaron and his sons,.... To the priestly office; this was done before, but is renewed for the confirmation of it, and repeated to put them in mind of it, that they be careful to execute it, as follows:and they shall wait on their priest's office, to do what was peculiar to it, both in the holy and in the most holy place, at the altar, and within, the vail, where the Levites had nothing to do; and this is observed that the priests might take notice, that by the gift of the Levites to them, they were not excused from doing any part of service which was proper to them as priests; for they were given them that they might more readily attend their office, and be wholly employed in it; just as, under the Gospel dispensation, deacons were appointed to take care of the secular affairs of the church, that the apostles might give up themselves to the word of God and prayer, Ac 6:2;and the stranger that cometh nigh shall be put to death; that comes nigh to perform any part of the priest's office peculiar to him as to offer sacrifice, burn incense, &c.