1 Chronicles 24:3

3 With the help of Zadok of the sons of Elea'zar, and Ahim'elech of the sons of Ith'amar, David organized them according to the appointed duties in their service.

1 Chronicles 24:3 Meaning and Commentary

1 Chronicles 24:3

And David distributed them
The posterities of Eleazar and Ithamar into certain classes or courses:

both Zadok of the sons of Eleazar, and Ahimelech of the sons of
Ithamar;
these were the two principal men of the respective families, the one was high priest, and the other "sagan" or deputy; or they both officiated as high priests alternately, until the one was removed in Solomon's time, and the other established alone. And now their brethren the priests, who were under each of these, are the persons David divided into classes:

according to their offices in their service:
to perform their office as priests in the service of the temple in their turns.

1 Chronicles 24:3 In-Context

1 The divisions of the sons of Aaron were these. The sons of Aaron: Nadab, Abi'hu, Elea'zar, and Ith'amar.

2 But Nadab and Abi'hu died before their father, and had no children, so Elea'zar and Ith'amar became the priests.

3 With the help of Zadok of the sons of Elea'zar, and Ahim'elech of the sons of Ith'amar, David organized them according to the appointed duties in their service.

4 Since more chief men were found among the sons of Elea'zar than among the sons of Ith'amar, they organized them under sixteen heads of fathers' houses of the sons of Elea'zar, and eight of the sons of Ith'amar.

5 They organized them by lot, all alike, for there were officers of the sanctuary and officers of God among both the sons of Elea'zar and the sons of Ith'amar.