1 Chronicles 24:3

3 David, together with Tzadok from the descendants of El'azar, and Achimelekh from the descendants of Itamar, arranged them in divisions for 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 descendants of Aharon were as follows: The sons of Aharon: Nadav, Avihu, El'azar and Itamar.

2 But Nadav and Avihu died before their father and had no children; therefore El'azar and Itamar functioned as the cohanim.

3 David, together with Tzadok from the descendants of El'azar, and Achimelekh from the descendants of Itamar, arranged them in divisions for service.

4 There were more men who were chiefs found among the descendants of El'azar than among the descendants of Itamar; therefore there were sixteen divisions of the descendants of El'azar, headed by clan leaders, and eight divisions of the descendants of Itamar, according to their clans.

5 They were assigned [periods of service] by lot, the one group equally with the other, since both the descendants of El'azar and the descendants of Itamar had officers of the sanctuary and officers of God.