1 Chronicles 24:3

3 And David distributeth them, and Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, according to their office 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 And to the sons of Aaron [are] their courses: sons of Aaron [are] Nadab, and Abihu, Eleazar, and Ithamar,

2 and Nadab dieth, and Abihu, in the presence of their father, and they had no sons, and Eleazar and Ithamar act as priests.

3 And David distributeth them, and Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, according to their office in their service;

4 and there are found of the sons of Eleazar more for heads of the mighty men than of the sons of Ithamar; and they distribute them: Of the sons of Eleazar, heads for a house of fathers, sixteen; and of the sons of Ithamar, for a house of their fathers, eight.

5 And they distribute them, by lots, one with another, for princes of the sanctuary, and princes of God, have been of the sons of Eleazar, and of the sons of Ithamar.