1 Kings 1:8
But Zadok the priest, and Benaiah the son of Jehoiada, and Nathan the prophet, and Shimei, and Rei, and the mighty men which belonged to David, were not with Adonijah. But Zadok the priest, and Benaiah the son of Jehoiada, and Nathan the prophet, and Shimei, and Rei, and the mighty men which belonged to David, were not with Adonijah.
Zadok the priest, Benaiah the son of Jehoiada, Nathan the prophet, Shimei, Rei, and the mighty men which belonged to David did not join Adonijah but stayed apart from his gathering and attempt to make himself king. Their absence from Adonijah marks them as loyal to David's house and separate from his conspiracy. That conspiracy was against Solomon, whom God had appointed to succeed David. To be not with Adonijah was therefore to stand apart from rebellion and on the side of God's appointed succession.