The Philistines gathered all their armies at Aphek, and the Israelites set up camp by the spring in Jezreel. The Philistine rulers were marching out in their divisions of hundreds and thousands with David and his men at the rear with King Achish. But the Philistine commanders asked, “What are these Hebrews doing here?”* This could also be translated, “Who are these Hebrews?” since the text simply says “What these Hebrews?”
Achish replied to the Philistine commanders, “That's David, an officer of King Saul of Israel. He's been with me for a long time, years even, and I haven't found any fault in him since the day he came over to our side up till now.”
But the Philistine commanders got angry with Achish, and told him, “Send him back to the place he came from, to the town you assigned to him. He can't go with us into battle. What if he turns on us during the fighting? What a great way for him to please his master—by handing over the heads of our men! Isn't this the David they sing about in their dances: ‘Saul has killed his thousands, and David his tens of thousands’?”
So Achish called David over and told him, “As the Lord lives, you are honest and you've done what's right as far as I can see. As far as I'm concerned you should march with me into battle because I haven't found any fault in you from the day you arrived until now. But the other leaders don't approve of you. So go back home in peace, and that way you won't do anything to upset the Philistine leaders.”
“But what have I done?” David asked. “What fault have you found in me, your servant, from the day I came to you until now, that would prevent me from going to fight the enemies of my lord the king?”
“As far as I'm concerned, you're as good as an angel of God,” Achish replied. “But the Philistine commanders have stated, ‘He can't go into battle with us.’ 10 So get up early tomorrow morning and leave with your men as soon as it's light.” 11 David and his men got up early in the morning and went back to the country of the Philistines. But the Philistines advanced on Jezreel.

*29:3 This could also be translated, “Who are these Hebrews?” since the text simply says “What these Hebrews?”