1 Samuel 27:10-12

10And Achish said, Against whom have ye 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 saved neither man nor woman alive, to bring them to Gath, saying, Lest they should tell of us, saying, So did David, and so hath been his manner all the while he hath dwelt in the country of the Philistines. 12And Achish believed David, saying, He hath made his people Israel utterly to abhor him; therefore he shall be my servant for ever.