1 Samuel 28:1-2

Now it came about in those days that the Philistines gathered their armed camps for war, to fight against Israel. And Achish said to David, “Know assuredly that you will go out with me in the camp, you and your men.” David said to Achish, “Very well, you shall know what your servant can do.” So Achish said to David, “Very well, I will make you my bodyguard for life.”