1 Samuel 27:8-12

8Now David and his men went up and raided the Geshurites, the Girzites and the Amalekites. (From ancient times these peoples had lived in the land extending to Shur and Egypt.) 9Whenever David attacked an area, he did not leave a man or woman alive, but took sheep and cattle, donkeys and camels, and clothes. Then he returned to Achish. 10When Achish asked, “Where did you go raiding today?” David would say, “Against the Negev of Judah” or “Against the Negev of Jerahmeel” or “Against the Negev of the Kenites.” 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.”