The Philistine commanders are angry with Achish for bringing David and his men with him to their camp at Aphek.1 Their explanation makes it clear that it should have been obvious to Achish that David was going to fight with Saul and not against him. They want David and his men to go away because they doubt their loyalties.2
They have no doubt about where David’s loyalties truly lie. With these words, the Philistines join a long line of witnesses to David’s loyalty. Jonathan (cf. 1 Samuel 19:4–5) and Samuel (1 Samuel 19:18–24), Ahimelech (1 Samuel 22:14) and Abigail (1 Samuel 25:28–31), Abner (cf. 1 Samuel 26:1–25) and Saul’s close attendants—there is a chorus of voices who all confirm: David is loyal to Saul. David was a true servant of his king.
4 But the commanders of the Philistines were angry with him. And the commanders of the Philistines said to him, “Send the man back, that he may return to the place to which you have assigned him. He shall not go down with us to battle, lest in the battle he become an adversary to us. For how could this fellow reconcile himself to his lord? Would it not be with the heads of the men here?