1 Samuel 27:10-12

10So Achish said, Have ye not made a raid to-day? And David said, Against the south of Judah, and against the south of the Jerahmeelites, and against the south of the Kenites. 11And David left neither man nor woman alive, to bring [them] to Gath, for he said, Lest they should tell of us, saying, So did David. And such was his custom as long as he abode in the country of the Philistines. 12And Achish trusted David, saying, He has made himself utterly odious among his people Israel; and he shall be my servant for ever.