1st Chronicles Chapter 23 American Standard-ASV1901
The sons of Amram: Aaron and Moses; and Aaron was separated, that he should sanctify the most holy things, he and his sons, for ever, to burn incense before Jehovah, to minister unto him, and to bless in his name, for ever.
These were the sons of Levi after their fathers' houses, even the heads of the fathers' `houses' of those of them that were counted, in the number of names by their polls, who did the work for the service of the house of Jehovah, from twenty years old and upward.
For their office was to wait on the sons of Aaron for the service of the house of Jehovah, in the courts, and in the chambers, and in the purifying of all holy things, even the work of the service of the house of God;
for the showbread also, and for the fine flour for a meal-offering, whether of unleavened wafers, or of that which is baked in the pan, or of that which is soaked, and for all manner of measure and size;
and to offer all burnt-offerings unto Jehovah, on the sabbaths, on the new moons, and on the set feasts, in number according to the ordinance concerning them, continually before Jehovah;
and that they should keep the charge of the tent of meeting, and the charge of the holy place, and the charge of the sons of Aaron their brethren, for the service of the house of Jehovah.