And to Aaron were born Nadab and Abihu, Eleazar and Ithamar.

David, Zadok (a descendant of Eleazar), and Ahimelech (a descendant of Ithamar) divided them into groups to carry out their assigned responsibilities. ¹ 

from the descendants of Phinehas, Gershom; from the descendants of Ithamar, Daniel; from the descendants of David, Hattush

The descendants of Eleazar had more leaders than the descendants of Ithamar, so they divided them up accordingly; the descendants of Eleazar had sixteen leaders, while the descendants of Ithamar had eight. ¹ 

This is the inventory ¹  of the tabernacle, the tabernacle of the testimony, which was counted ²  by the order ³  of Moses, being the work ⁴  of the Levites under the direction ⁵  of Ithamar, son of Aaron the priest.

Later Moses sought diligently for the sin offering male goat, ¹  but it had actually been burnt. ²  So he became angry at Eleazar and Ithamar, Aaron’s remaining sons, saying,

This is the service of the families of the Gershonites concerning the tent of meeting. Their responsibilities will be under the authority ¹  of Ithamar son of Aaron the priest. ² 

This is the service of the families of the Merarites, their entire service concerning the tent of meeting, under the authority of Ithamar son of Aaron the priest.”

and he gave four carts and eight oxen to the Merarites, as their service required, under the authority ¹  of Ithamar son of Aaron the priest.

They divided them by lots, for there were officials of the holy place and officials designated by God among the descendants of both Eleazar and Ithamar. ¹ 

Aaron married Elisheba, the daughter of Amminadab and sister of Nahshon, and she bore him Nadab and Abihu, Eleazar and Ithamar.

Then Moses spoke to Aaron and to Eleazar and Ithamar, his remaining sons, “Take the grain offering which remains from the gifts of the Lord and eat it unleavened beside the altar, for it is most holy.