1 Chronicles 23:3, 24, 26-27

The Levites, thirty years old and upward, were numbered, and the total was 38,000 men.

These were the sons of Levi by their fathers’ houses, the heads of fathers’ houses as they were listed according to the number of the names of the individuals from twenty years old and upward who were to do the work for the service of the house of the LORD.

And so the Levites no longer need to carry the tabernacle or any of the things for its service.” For by the last words of David the sons of Levi were numbered from twenty years old and upward.