Ithamar
Archimandrite Nikifor’s Biblical Encyclopedia
(land of palms) (Exod 6:23; 28:1; Lev 10:16) - Aaron's fourth son. After the death of his brothers Nadab and Abihu, he and his elder brother Eleazar were called to priestly service. During the Hebrews' wandering in the Arabian wilderness, he was entrusted with chief oversight of the sons of Gershon and Merari (Exod 38:21; Num 4:21-33), and under his supervision the Levites made an accounting of what had been used to construct the tabernacle. When the divisions for temple service were assigned, Eleazar had more family heads than Ithamar; therefore eight courses were appointed from Ithamar's family and sixteen from Eleazar's (1 Chr 24).
The high priesthood ordinarily remained hereditary in the senior line, with the exception of Eli, who, as is known, descended from the house of Ithamar and became high priest for an unknown reason. Under Abiathar, however, who sided with Adonijah, the high priesthood returned to Eleazar's house in accordance with Samuel's prophecy (1 Sam 2:35; 1 Kings 2:26-27). One of Ithamar's descendants, Daniel, returned from the Babylonian captivity with Ezra (Ezra 8:2).