1 Samuel 29:2-3

2As the Philistine rulers were leading out their troops in groups of hundreds and thousands, David and his men marched at the rear with King Achish.

3But the Philistine commanders demanded, “What are these Hebrews doing here?” And Achish told them, “This is David, the servant of King Saul of Israel. He’s been with me for years, and I’ve never found a single fault in him from the day he arrived until today.”