Zadok and Abiathar... the priests. — Abiathar, though disgraced and practically deposed, was still regarded theoretically as priest (much as Annas is called “high priest” in the Gospels), for the priesthood was properly for life.
Related Commentaries of 1 Kings 4:4
1 Kings 4:4
4 And Benaiah the son of Jehoiada was over the host: and Zadok and Abiathar were the priests: