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.

Cross-reference

In 1 Chronicles 23:24, the Levites are counted for service — setting the precedent for the priestly divisions here.

Numbers 25:11–13 Historical context

Numbers 25:11-13 gives Phinehas's covenant of perpetual priesthood—explaining why Eleazar's line had more chief men than Ithamar's here.

In 2 Samuel 8:17, Zadok and Ahimelech are named as priests — showing the historical leaders of the Eleazar and Ithamar lines.