Albert Barnes Commentary 1 Kings 1:32

"And king David said, Call to me Zadok the priest, and Nathan the prophet, and Benaiah the son of Jehoiada. And they came before the king." — 1 Kings 1:32 (ASV)

The combination of the high priest, the prophet, and the captain of the bodyguard (the Cherethites and Pelethites, 1 Kings 1:38) would show the people that the proceedings had the king’s sanction. The order of the names indicates the position of each person in this matter.