Numbers 8:22-24

Revised Standard Version

²² And after that the Levites went in to do their service in the tent of meeting in attendance upon Aaron and his sons; as the Lord had commanded Moses concerning the Levites, so they did to them.

²³ And the Lord said to Moses, ²⁴ “This is what pertains to the Levites: from twenty-five years old and upward they shall go in to perform the work in the service of the tent of meeting;