1 Then the Philistines gathered together all their armies at Aphek, and the Israelites encamped by a fountain which is in Jezreel. 2 And the lords of the Philistines passed in review by hundreds and by thousands, but David and his men passed in review at the rear with Achish. 3 Then the princes of the Philistines said, “What are these Hebrews doing here?” And Achish said to the princes of the Philistines, “Is this not David, the servant of Saul king of Israel, who has been with me these days, or these years? And to this day I have found no fault in him since he defected to me.” 4 But the princes of the Philistines were angry with him; so the princes of the Philistines said to him, “Make this fellow return, that he may go back to the place which you have appointed for him, and do not let him go down with us to battle, lest in the battle he become our adversary. For with what could he reconcile himself to his master, if not with the heads of these men? 5 Is this not David, of whom they sang to one another in dances, saying: ‘Saul has slain his thousands, And David his ten thousands’?”
“‘Then the Philistines gathered together all their armies at Aphek, and the Israelites encamped by a fountain which is in Jezreel.” “This fountain is the present Ain Jalûd (or Ain Jalût , i.e., Goliath's fountain, probably so called because it was regarded as the scene of the defeat of Goliath), a very large fountain, which issues from a cleft in the rock at the foot of the mountain on the north-eastern border of Gilboa, forming a beautifully limpid pool of about forty or fifty feet in diameter, and then flowing in a brook through the valley (Rob. Pal . iii. p. 168). Consequently Aphek , which must be carefully distinguished from the towns of the same name in Asher (Joshua 19:30; Judges 1:31) and upon the mountains of Judah (Joshua 15:53) and also at Ebenezer (1 Samuel 4:1), is to be sought for not very far from Shunem , in the plain of Jezreel; according to Van de Velde's Mem ., by the side of the present el Afûleh …” (Keil & Delitzsch)— “And the lords of the Philistines passed in review by hundreds and by thousands,’— Lustrabrant exercitum, they made a general muster, and took a view of their forces, by their several companies, regiments, and brigades. ‘But David and his men passed in review at the rear with Achish,’ whom they had chosen general; wherefore also he brought up the rear, having David and his men for his bodyguard,” (Trapp)
The Philistines princes could not stomach this mixture and said, “Make this fellow return, that he may go back to the place which you have appointed for him, and do not let him go down with us to battle, lest in the battle he become our adversaryFor with what could he reconcile himself to his master, if not with the heads of these men? etc.” “The presence of David gave umbrage to the princes. Conscious of his superior valour from past experiment, perhaps they were secretly jealous that he would eclipse their glory; but they artfully preferred their objection on the ground of suspicion.” (Joseph Sutcliffe)— “Is this not David, of whom they sang to one another in dances, saying: ‘Saul has slain his thousands, And David his ten thousands’?”
6 Then Achish called David and said to him, “Surely, as the Lord lives, you have been upright, and your going out and your coming in with me in the army is good in my sight. For to this day I have not found evil in you since the day of your coming to me. Nevertheless the lords do not favor you. 7 Therefore return now, and go in peace, that you may not displease the lords of the Philistines.” 8 So David said to Achish, “But what have I done? And to this day what have you found in your servant as long as I have been with you, that I may not go and fight against the enemies of my lord the king?” 9 Then Achish answered and said to David, “I know that you are as good in my sight as an angel of God; nevertheless the princes of the Philistines have said, ‘He shall not go up with us to the battle.’ 10 Now therefore, rise early in the morning with your master’s servants who have come with you. And as soon as you are up early in the morning and have light, depart.” 11 So David and his men rose early to depart in the morning, to return to the land of the Philistines. And the Philistines went up to Jezreel
“Surely, as Jehovah lives”— “It is very remarkable that Achish should swear by Jehovah. David, it would seem, had converted him to this confession of faith; and therefore he regarded David as an angel of God, as he says, 1 Samuel 29:9.” (Joseph Sutcliffe)— “you have been upright, and your going out and your coming in with me in the army is good in my sight,’ his entire behavior at all times had met with the approval of the Philistine king; ‘for to this day I have not found evil in you since the day of your coming to me; nevertheless the lords do not favor you,’ they refused to drop their suspicions against him.” (The Popular Commentary by Paul E. Kretzmann)
‘Therefore return now, and go in peace, that you may not displease the lords of the Philistines.’
“David scarcely ever had a greater deliverance than when dismissed from such insnaring service.” (Matthew Henry) “Surely none but a wise God could have found the means to have brought him out of the double danger into which his folly and sin had brought him. Apparently there was no way to escape, but either he must have proved a traitor to his country, or a traitor to his friend. And surely none but a faithful God would have given grace to have brought him out," (Hawker's Poor Man's Commentary) when his own disbelief had caused the predicament he found himself in.