1 Samuel 27:11-12

11He did not leave a man or woman alive to be brought to Gath, for he thought, “They might inform on us and say, ‘This is what David did.’ ” And such was his practice as long as he lived in Philistine territory. 12Achish trusted David and said to himself, “He has become so obnoxious to his people, the Israelites, that he will be my servant for life.”