1 Samuel 27:1-2

And David said in his heart, I shall now perish one day by the hand of Saul: there is nothing better for me than that I should speedily escape into the land of the Philistines; and Saul shall despair of me, to seek me any more in any coast of Israel: so shall I escape out of his hand. And David arose, and he passed over with the six hundred men that were with him unto Achish, the son of Maoch, king of Gath.