I Samuel 27:4

First Samuel 27 records David's despair that Saul would one day kill him, so he escapes with his six hundred men to the land of the Philistines and dwells with Achish king of Gath, after which Saul stops pursuing him. David and his men settle in Gath and then in Ziklag, and David conducts raids against the Geshurites, Girzites, and Amalekites, leaving no survivors so Achish will not hear what he has done. Achish trusts David, believing he has made himself utterly loathsome among his own people Israel and will therefore be his servant forever.