Ithamar is first mentioned in Exodus 6:23 as one of four sons of Aaron the priest, Moses’ brother. Aaron’s sons—Nadab, Abihu, Eleazar, and Ithamar—also served as priests to the Lord (Exodus 28:1). According to Numbers 3:2, Ithamar was most likely the youngest son. Although the Bible does not often mention the names of mothers, it does in Ithamar’s case. Aaron had married a woman named Elishiba, the daughter of a man named Amminadab. This is significant because we learn from the genealogy in the book of Ruth that Amminadab was also the great-grandfather of Boaz (Ruth 4:19–21). So Ithamar was a distant relative of Boaz and eventually of King David (Ruth 20:22).
Ithamar is mentioned again in Leviticus 10. Aaron’s two older sons, acting in their priestly roles, desecrated God’s holiness by offering “strange fire” to the Lord. For this act of blatant disobedience, the Lord struck them both dead. The Lord then instructed Aaron and his two remaining sons, Eleazar and Ithamar, not to mourn for their brothers and sons, although the rest of the camp could do so (Leviticus 10:6). While this seems a harsh order, it could be that Eleazar and Ithamar had already been consecrated as active priests and were in their season of serving, and they could not set that role aside to grieve for two men whom the Lord had judged.
Moses explained God’s reason for killing Nadab and Abihu: “Among those who approach me I will be proved holy; in the sight of all the people I will be honored” (Leviticus 10:3). Later, the Lord Himself spoke to Aaron, explaining why priests must adhere to all God had commanded them. He said it was so that the Israelites would learn to “distinguish between the holy and the common, between the unclean and the clean, and so you can teach the Israelites all the decrees the Lord has given them through Moses” (verses 10–11). We can assume that this tragic event made a strong impression on Aaron’s remaining sons, and they served the Lord faithfully as priests from then on (1 Chronicles 24:2).
Ithamar’s specific assignment was to oversee the clans of Levites called the Gershonites and the Merarites (Numbers 3:28, 33). The Gershonites, under the direction of Ithamar, were “to carry the curtains of the tabernacle, that is, the tent of meeting, its covering and its outer covering of durable leather, the curtains for the entrance to the tent of meeting, the curtains of the courtyard surrounding the tabernacle and altar, the curtain for the entrance to the courtyard, the ropes and all the equipment used in the service of the tent” (Numbers 4:25–26). The Merarites were “to carry the frames of the tabernacle, its crossbars, posts and bases, as well as the posts of the surrounding courtyard with their bases, tent pegs, ropes, all their equipment and everything related to their use” (Numbers 4:31–32).
Because Ithamar remained faithful to his God, unlike his brothers who had the same opportunities, Aaron’s priestly line continued through him. Five high priests, beginning with Eli, were descendants of Ithamar, but most of the high priests were from his brother Eleazar’s line. While two of his older brothers chose dishonor, Ithamar chose to honor the Lord, and his name is recorded in Scripture as a faithful priest of the Lord.