1 Chronicles 23:4, 24

Of these, 24,000 were to oversee the work of the house of the LORD; and 6,000 were officers and judges

These were the sons of Levi according to their fathers’ households, even the heads of the fathers’ households of those of them who were counted, in the number of names by their census, doing the work for the service of the house of the LORD, from twenty years old and upward.