Numbers 3:6-16

6“Bring the tribe of Levi near and present them before Aaron the priest, so that they may serve him.

7They shall carry out the duties for him and for the whole congregation before the Tent of Meeting, doing the service of the tabernacle.

8They shall also take care of all the furnishings and utensils of the Tent of Meeting, and [attend to] the duties of the Israelites, doing the service of the tabernacle.

9You shall give the Levites to Aaron and to his sons [as servants and helpers]; they are to be given wholly to him from among the Israelites.

10So you shall appoint Aaron and his sons, and they shall observe and attend to their priesthood; but the layman (non-Levite) who approaches [the holy things] shall be put to death.”

11Again the Lord spoke to Moses, saying,

12“Behold, I have taken the Levites from among the sons of Israel instead of and as a substitute for every firstborn, that is, the first that opens the womb among the Israelites. So the Levites shall be Mine,

13for all the firstborn are Mine. On the day that I killed all the firstborn in the land of Egypt, I consecrated for Myself all the firstborn in Israel, both man and animal. They shall be mine; I am the Lord.”

14Then the Lord spoke to Moses in the Wilderness of Sinai, saying,

15“Number the sons of Levi by their fathers’ households, by their families (clans). You shall number every male from a month old and upward.”

16So Moses numbered them just as he was commanded by the word (mouth) of the Lord.