Numbers 8:20-26 - The Levites Are Dedicated To The Lord
20 Moses, Aaron, and all the people of Israel dedicated the Levites, as Jehovah commanded Moses. 21 So the Levites purified themselves and washed their clothes. Aaron dedicated them as a special gift to Jehovah. He also performed the ritual of purification for them. 22 The people did everything Jehovah commanded Moses concerning the Levites. Thus the Levites were qualified to work in the tent under Aaron and his sons.
23 Jehovah said to Moses: 24 From the age of twenty-five each Levite shall perform his duties in the tent of my presence, 25 They must retire from active service when they are fifty years old. 26 They may assist the other Levites in their duties at the tent of meeting. But they may not do any regular work. This is how you will handle the Levites' duties.