Thematic Bible: Is refused permission to accompany the philistines to battle against the israelites

Now in those days the Philistines got their forces together to make war on Israel. And Achish said to David, Certainly you and your men are to go out with me to the fight. And David said to Achish, You will see now what your servant will do. And Achish said to David, Then I will make you keeper of my head for ever.