1 Chronicles 23:24-27

24These were the sons of Levi after their fathers’ houses, even the heads of the fathers’ houses of those of them that were counted, in the number of names by their polls, who did the work for the service of the house of the LORD, from twenty years old and upward.

25For David said, The LORD, the God of Israel, hath given rest unto his people; and he dwelleth in Jerusalem for ever:

26and also the Levites shall no more have need to carry the tabernacle and all the vessels of it for the service thereof.

27For by the last words of David the sons of Levi were numbered, from twenty years old and upward.