1 Chronicles 24:4
And there were more chief men found of the sons of Eleazar than of the sons of Ithamar; and thus were they divided. Among the sons of Eleazar there were sixteen chief men of the house of their fathers, and eight among the sons of Ithamar according to the house of their fathers.
David divided the descendants of Eleazar and Ithamar into twenty-four priestly courses. Sixteen chief men were counted from Eleazar's line according to the house of their fathers, and eight from Ithamar's line on the same basis. The apportionment followed family lines and recognized leadership, forming part of a carefully ordered arrangement for sanctuary service.