Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
1 Kings (1 Samuel) 29:1
Whilst Saul derived no comfort from his visit to the witch at Endor, but simply heard from the mouth of Samuel the confirmation of his rejection on the part of God, and an announcement of his approaching fate, David was delivered, through the interposition of God, from the danger of having to fight against his own people.
The account of this is introduced by a fuller description of the position of the hostile army. "The Philistines gathered all their armies together towards Aphek, but Israel encamped at the fountain in (at) Jezreel." This fountain is the present Ain Jald (or Ain Jalt, 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 (Jos 19:30; Jdg 1:31) and upon the mountains of Judah (Jos 15:53) and also at Ebenezer (Sa1 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 Afleh, though the situation has not been exactly determined. The statement in the Onom., "near Endor of Jezreel where Saul fought," is merely founded upon the Septuagint, in which בּעין is erroneously rendered ἐν Ἐνδώρ.
When the princes of the Philistines (sarne, as in Jos 13:3) advanced by hundreds and thousands (i.e., arranged in companies of hundreds and thousands), and David and his men came behind with Achish (i.e., forming the rear-guard), the (other) princes pronounced against their allowing David and his men to go with them. The did not occur at the time of their setting out, but on the road, when they had already gone some distance (compare Sa1 29:11 with Sa1 30:1), probably when the five princes (Jos 13:3) of the Philistines had effected a junction. To the inquiry, "What are these Hebrews doing?" Achish replied, "Is not this David, the servant of Saul the king of Israel, who has been with me days already, or years already? and I have found nothing in him since his coming over unto this day." מאוּמה, anything at all that could render his suspicious, or his fidelity doubtful. נפל, to fall away and go over to a person; generally construed with אל (Jer 37:13; Jer 38:19, etc.) or על (Jer 21:9; Jer 37:14; Ch1 12:19-20), but here absolutely, as the more precise meaning can be gathered from the context.
But the princes, i.e., the four other princes of the Philistines, not the courtiers of Achish himself, were angry with Achish, and demanded, "Send the man back, that he may return to his place, which thou hast assigned him; that he may not go down with us into the war, and may not become an adversary (satan) to us in the war; for wherewith could he show himself acceptable to his lord (viz., Saul), if not with the heads of these men?" הלוא, nonne, strictly speaking, introduces a new question to confirm the previous question. "Go down to the battle:" this expression is used as in Sa1 26:10; Sa1 30:24, because battles were generally fought in the plains, into which the Hebrews were obliged to come down from their mountainous land. "These men," i.e., the soldiers of the Philistines, to whom the princes were pointing.
To justify their suspicion, the princes reminded him of their song with which the women in Israel had celebrated David's victory over Goliath (Sa1 18:7).
1 Kings (1 Samuel) 29:6
After this declaration on the part of the princes, Achish was obliged to send David back.
With a solemn assertion, - swearing by Jehovah to convince David all the more thoroughly of the sincerity of his declaration, - Achish said to him, "Thou art honourable, and good in my eyes (i.e., quite right in my estimation) are thy going out and coming in (i.e., all thy conduct) with me in the camp, for I have not found anything bad in thee; but in the eyes of the princes thou art not good (i.e., the princes do not think thee honourable, do not trust thee). Turn now, and go in peace, that thou mayest do nothing displeasing to the princes of the Philistines."
Partly for the sake of vindicating himself against this suspicion, and partly to put the sincerity of Achish's words to the test, David replied, "What have I done, and what hast thou found in thy servant, since I was with thee till this day, that I am not to come and fight against the enemies of my lord the king?" These last words are also ambiguous, since the king whom David calls his lord might be understood as meaning either Achish or Saul. Achish, in his goodness of heart, applies them without suspicion to himself; for he assures David still more earnestly (Sa1 29:9), that he is firmly convinced of his uprightness. "I know that thou art good in my eyes as an angel of God," i.e., I have the strongest conviction that thou hast behaved as well towards me as an angel could; but the princes have desired thy removal.
"And now get up early in the morning with the servants of thy lord (i.e., Saul, whose subjects David's men all were), who have come with thee; get ye up in the morning when it gets light for you (so that ye can see), and go."
In accordance with this admonition, David returned the next morning into the land of the Philistines, i.e., to Ziklag; no doubt very light of heart, and praising God for having so graciously rescued him out of the disastrous situation into which he had been brought and not altogether without some fault of his own, rejoicing that "he had not committed either sin, i.e., had neither violated the fidelity which he owed to Achish, nor had to fight against the Israelites" (Seb. Schmidt).