1 Samuel 29:6-7
29:6 So Achish called David and said to him, “As surely as the LORD lives, you have been reliable, and I would be pleased to have you serve with me in the army. From the day you came to me until now, I have found no fault in you, but the rulers [other rulers of the Philistines] don’t approve of you.

29:7 Turn back and go in peace [David thus protected from having to accompany the Philistines in their fight against Israel]; do nothing to displease the Philistine rulers.”