David Musters with the Philistines

1 Samuel 28:1-2

And it came to pass in those days, that the Philistines gathered together their armies, to be prepared for war against Israel: And Achis said to David: Know thou now assuredly, that thou shalt go out with me to the war, thou, and thy men.

And David said to Achis: Now thou shalt know what thy servant will do. And Achis said to David: And I will appoint thee to guard my life for ever.