Here we read of God's first intervention. ‘Then said the princes of the Philistines, What do these Hebrews here?’ The princes are wary of David and his men.
We can get into that kind of position by trusting worldly things, getting ourselves into worldliness. This is what led to David's impossible position. But I think he must have hoped and prayed that while Achish wanted him to engage on the Philistine side against Israel, that the other lords of the Philistines, once they heard about it, wouldn't permit it, wouldn't stand for it. Fortunately for David, by the superintendency of God in these affairs, that is exactly what happened. Although David had taken up a position, nervously, at the very back of their armies, he is sent away.
Why didn't they just execute David? Why didn't they just finish him? Why merely insist or plead for his being sent back? That is a mark God's preserving hand, even in his backslidden servant David. The love of God is still upon him. The doctrine of the perseverance of the saints is going to play out in this passage.