Radak

The kings of the land take their stand: – for all the satraps of the Philistines had taken their stand with one consent and in agreement to come to fight with David. And he calls them “kings” and “rulers,” although we have not seen any other passage where he describes them otherwise than as “satraps” of the Philistines, who in their pride were imagining themselves kings, though they were not so. Possibly also there were assembled with them other kings from the nations. And rulers take counsel (יַוסדו) together: – They had all consulted together as one. Counsel also is expressed in the word יסוד (foundation), for counsel is to actual performance as the foundation to a building. Against the Lord and against His anointed: – for they knew that David was king by the appointment of the Lord, and Samuel the prophet of the Lord had anointed him king.