17. Every firstborn male in Israel, whether human or animal, is mine. When I struck down all the firstborn in Egypt, I set them apart for myself.
18. And I have taken the Levites in place of all the firstborn sons in Israel.
19. From among all the Israelites, I have given the Levites as gifts to Aaron and his sons to do the work at the tent of meeting on behalf of the Israelites and to make atonement for them so that no plague will strike the Israelites when they go near the sanctuary.’
20. Moses, Aaron and the whole Israelite community did with the Levites just as the Lord commanded Moses.
21. The Levites purified themselves and washed their clothes. Then Aaron presented them as a wave offering before the Lord and made atonement for them to purify them.
22. After that, the Levites came to do their work at the tent of meeting under the supervision of Aaron and his sons. They did with the Levites just as the Lord commanded Moses.
23. The Lord said to Moses,
24. ‘This applies to the Levites: men twenty-five years old or more shall come to take part in the work at the tent of meeting,
25. but at the age of fifty, they must retire from their usual duties and work no longer.
26. They may assist their brothers in performing their duties at the tent of meeting, but they themselves must not do the work. This, then, is how you are to assign the responsibilities of the Levites.’