Aaron, the brother of Moses, was the first high priest of Israel, and his descendants played a significant role in the religious and communal life of the Israelites. The lineage of Aaron is central to the priestly tradition in the Hebrew Bible, as his descendants were designated as the priestly class, responsible for performing sacrifices and maintaining the sanctuary.

Lineage and Role:
Aaron had four sons: Nadab, Abihu, Eleazar, and Ithamar (Exodus 6:23). Nadab and Abihu, the eldest sons, died without offspring when they offered unauthorized fire before the LORD (Leviticus 10:1-2). This left Eleazar and Ithamar to carry on the priestly duties.

Eleazar:
Eleazar succeeded Aaron as high priest. He played a crucial role during the Israelites' journey through the wilderness and into the Promised Land. Numbers 20:25-28 describes the transfer of the high priesthood from Aaron to Eleazar. Eleazar's descendants continued the high priestly line, with his son Phinehas noted for his zealousness in Numbers 25:11-13, where God made a covenant of peace with him, promising a lasting priesthood.

Ithamar:
Ithamar's descendants also served in the priesthood, though they did not hold the high priestly office as prominently as Eleazar's line. Notably, Eli, a priest during the time of Samuel, was from the line of Ithamar (1 Samuel 2:27-36). However, due to the sins of Eli's sons, a prophecy declared the end of his family's priestly line.

Division of Priestly Duties:
During King David's reign, the priestly duties were organized into divisions. 1 Chronicles 24:1-19 details the division of the priests into 24 groups, with both Eleazar's and Ithamar's descendants represented. This organization ensured a systematic rotation of priestly service in the temple.

Post-Exilic Period:
After the Babylonian exile, the descendants of Aaron returned to Jerusalem and resumed their priestly functions. Ezra 2:36-39 lists the families of priests who returned, including those from the lines of Jedaiah, Immer, Pashhur, and Harim, all of whom were descendants of Aaron.

Significance:
The descendants of Aaron were integral to the religious life of Israel, serving as mediators between God and the people. Their role was not only to perform sacrifices but also to teach the law and maintain the sanctity of worship. The Aaronic priesthood is a central theme in the Old Testament, symbolizing the covenant relationship between God and Israel.

Biblical References:
· Exodus 6:23: "Aaron married Elisheba, daughter of Amminadab and sister of Nahshon, and she bore him Nadab, Abihu, Eleazar, and Ithamar."
· Leviticus 10:1-2: "Now Aaron’s sons Nadab and Abihu took their censers, put fire in them and added incense, and they offered unauthorized fire before the LORD, contrary to His command. So fire came out from the presence of the LORD and consumed them, and they died before the LORD."
· Numbers 20:25-28: "Take Aaron and his son Eleazar and bring them up Mount Hor. Remove Aaron’s garments and put them on his son Eleazar. Aaron will be gathered to his people and will die there."
· Numbers 25:11-13: "Phinehas son of Eleazar, the son of Aaron the priest, has turned My wrath away from the Israelites by being as zealous among them as I was. So I did not put an end to them in My zeal. Therefore tell him I am making My covenant of peace with him. It will be a covenant of a lasting priesthood, because he was zealous for the honor of his God and made atonement for the Israelites."
· 1 Samuel 2:27-36: The prophecy against Eli's house.
· 1 Chronicles 24:1-19: The division of the priests.
· Ezra 2:36-39: The list of returning priests.