1 Chronicles 24:2-6

But Nadab and Abihu died before their father and had no sons. So Eleazar and Ithamar served as priests.

David, with Zadok of the sons of Eleazar and Ahimelech of the sons of Ithamar, divided them according to their offices for their ministry.

Since more chief men were found from the descendants of Eleazar than the descendants of Ithamar, they divided them this way: there were sixteen heads of fathers’ households of the descendants of Eleazar, and eight of the descendants of Ithamar according to their fathers’ households.

So they were divided by lot, the one as the other; for they were officers of the sanctuary and officers of God, both from the descendants of Eleazar and the descendants of Ithamar.

Shemaiah, the son of Nethanel the scribe, from the Levites, recorded them in the presence of the king, the leaders, Zadok the priest, Ahimelech the son of Abiathar, and the heads of the fathers’ households of the priests and the Levites; one father’s household taken for Eleazar and one taken for Ithamar.