C. F. Keil and Franz Delitzsch on 1 Samuel 26:21

1Sa 26:21

Moreover, Saul could not help confessing, “I have sinned: return, my son David; I will do thee harm no more, because my life was precious in thine eyes that day.” A good intention, which he never carried out. “He declared that he would never do any more what he had already so often promised not to do again; and yet he did not fail to do it again and again. He ought rather to have taken refuge with God, and appealed to Him for grace, that he might not fall into such sins again; yea, he should have entreated David himself to pray for him” (Berleb. Bible). He adds still further, “Behold, I have acted foolishly, and have gone sore astray;” but yet he persists in this folly. “There is no sinner so hardened, but that God gives him now and then some rays of light, which show him all his error. But, alas! when they are awakened by such divine movings, it is only for a few moments; and such impulses are no sooner past, than they fall back again immediately into their former life, and forget all that they have promised.”