1 Samuel 27:12

12And Achish trusted David, thinking, “He has made himself an utter stench to his people Israel; therefore he shall always be my servant.”

1 Samuel 29:2-3

2As athe lords of the Philistines were passing on by hundreds and by thousands, and David and his men were passing on in the rear bwith Achish, 3the commanders of the Philistines said, “What are these Hebrews doing here?” And Achish said to the commanders of the Philistines, “Is this not David, the servant of Saul, king of Israel, who has been with me cnow for days and years, and since he deserted to me dI have found no fault in him to this day.”
Copyright information for ESV