Priests: Divided by David Into Twenty-Four Courses

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

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.

Prepare yourselves by families in your divisions, according to the instructions written by David king of Israel and Solomon his son.

Moreover, stand in the Holy Place by the divisions of the families of your kinsmen the lay people, and by the divisions of the families of the Levites.