These were the divisions of the descendants of Aaron. The sons of Aaron were Nadab, Abihu, Eleazar, and Ithamar.

Exodus 6:23
And Aaron married Elisheba, the daughter of Amminadab and sister of Nahshon, and she bore him Nadab and Abihu, Eleazar and Ithamar.

1 Chronicles 28:13
for the divisions of the priests and Levites, for all the work of service in the house of the LORD, and for all the articles of service in the house of the LORD:

2 Chronicles 5:11
Now all the priests who were present had consecrated themselves regardless of their divisions. And when the priests came out of the Holy Place,

2 Chronicles 8:14
In keeping with the ordinances of his father David, Solomon appointed the divisions of the priests over their service, and the Levites for their duties to offer praise and to minister before the priests according to the daily requirement. He also appointed gatekeepers by their divisions at each gate, for this had been the command of David, the man of God.

2 Chronicles 23:8
So the Levites and all Judah did everything that Jehoiada the priest had ordered. Each of them took his men--those coming on duty on the Sabbath and those going off duty--for Jehoiada the priest had not released any of the divisions.

2 Chronicles 31:2
Hezekiah reestablished the divisions of the priests and Levites--each of them according to their duties as priests or Levites--for the burnt offerings and peace offerings, for ministry, for giving thanks, and for singing praises at the gates of the LORD's dwelling.

Ezra 6:18
They also appointed the priests by their divisions and the Levites by their groups to the service of God in Jerusalem, according to what is written in the Book of Moses.

Now these are the divisions of the sons of Aaron. The sons of Aaron; Nadab, and Abihu, Eleazar, and Ithamar.