David becomes Achish’s bodyguard
The Philistines gathered to go to war against Israel, and David became Achish’s bodyguard.
Key passages
1 Sa 28:1–2

Now in those days the Philistines gathered their forces for war to fight against Israel. So Achish said to David, “Certainly you realize that you must go out with me in the army, you and your men.” David said to Achish, “Very well, you will know what your servant can do.” Achish said to David, …

1 Sa 28:4

Then the Philistines assembled and came and encamped at Shunem, so Saul assembled all Israel, and they encamped at Gilboa.