Easton's Bible Dictionary

Ithamar - palm isle, the fourth and youngest son of Aaron (1 Chr. 6:3). He was consecrated to the priesthood along with his brothers (Ex. 6:23); and after the death of Nadab and Abihu, he and Eleazar alone discharged the functions of that office (Lev. 10:6, 12; Num. 3:4). He and his family occupied the position of common priest till the high priesthood passed into his family in the person of Eli (1 Kings 2:27), the reasons for which are not recorded. (See ZADOK)