John Gill Commentary 1 Samuel 24:18

"And thou hast declared this day how that thou hast dealt well with me, forasmuch as when Jehovah had delivered me up into thy hand, thou killedst me not." — 1 Samuel 24:18 (ASV)

And you have showed this day how that you have dealt well with me The cutting off of the skirt of his robe only, when his life was in his hand, was a clear proof and full demonstration of his dealing well with him, and might sufficiently convince him he had no ill design upon him: forasmuch as when the Lord had delivered me into your hand, you did not kill me ; this was a plain proof and evidence of his kindness to him, which he owns, and also the providence of God in this affair, which had delivered him into the hands of David; by which he might see the Lord was for David, and against him, and might have deterred him from seeking David's hurt hereafter; but it did not.