Numbers 8:22-24

New King James Version

^22 (A)After that the Levites went in to do their work in the tabernacle of meeting before Aaron and his sons; ^(B)as the Lord commanded Moses concerning the Levites, so they did to them.

²³ Then the Lord spoke to Moses, saying, ²⁴ “This is what pertains to the Levites: ^(C)From twenty-five years old and above one may enter to perform service in the work of the tabernacle of meeting;