17. For every firstborn among the sons of Israel is Mine, among the men and among the animals; on the day that I struck down all the firstborn in the land of Egypt I sanctified them for Myself.
18. But I have taken the Levites instead of every firstborn among the sons of Israel.
19. I have given the Levites as a gift to Aaron and to his sons from among the sons of Israel, to perform the service of the sons of Israel at the tent of meeting and to make atonement on behalf of the sons of Israel, so that there will be no plague among the sons of Israel by their coming near to the sanctuary."
20. Thus did Moses and Aaron and all the congregation of the sons of Israel to the Levites; according to all that the Lord had commanded Moses concerning the Levites, so the sons of Israel did to them.
21. The Levites, too, purified themselves from sin and washed their clothes; and Aaron presented them as a wave offering before the Lord. Aaron also made atonement for them to cleanse them.
22. Then after that the Levites went in to perform their service in the tent of meeting before Aaron and before his sons; just as the Lord had commanded Moses concerning the Levites, so they did to them.
23. Now the Lord spoke to Moses, saying,
24. "This is what applies to the Levites: from twenty-five years old and upward they shall enter to perform service in the work of the tent of meeting.
25. But at the age of fifty years they shall retire from service in the work and not work any more.
26. They may, however, assist their brothers in the tent of meeting, to keep an obligation, but they themselves shall do no work. Thus you shall deal with the Levites concerning their obligations."