Numbers 8:21-24

Living Bible

²¹ The Levites purified themselves and washed their clothes, and Aaron presented them to the Lord in a gesture of offering. He then performed the rite of atonement over them to purify them. ²² After that they went into the Tabernacle as assistants to Aaron and his sons; everything was done just as the Lord had commanded Moses.

^23-24 The Lord also instructed Moses, “The Levites are to begin serving in the Tabernacle at the age of twenty-five, and are to retire at the age of fifty.