1 Chronicles 24:3, 6

With the help of Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, David organized them according to the appointed duties in their service.

And the scribe Shemaiah, the son of Nethanel, a Levite, recorded them in the presence of the king and the princes and Zadok the priest and Ahimelech the son of Abiathar and the heads of the fathers’ houses of the priests and of the Levites, one father’s house being chosen for Eleazar and one chosen for Ithamar.