1 Samuel 29:3-5

3the Philistine commanders [having noticed David] said, “What are these Hebrews doing here?” Achish said to the Philistine commanders, “Is this not David, the servant of Saul king of Israel, who has been with me these days and years, and I have found no fault in him from the day he deserted to me to this day?”

4But the Philistine commanders were angry with Achish and they said to him, “Make this man return, so that he may go back to his place where you have assigned him, and do not let him go down to battle with us, or in the battle he may [turn and] become our adversary. For how could David reconcile himself to his lord [Saul]? Would it not be with the heads of these [Philistine] men?

5Is this not David, of whom they used to sing in dances, ‘Saul killed his thousands, And David his ten thousands’?”