1 Samuel 15:11

It repenteth Me that I have set up Saul to be king, an expression which denotes that God had found it necessary to change His mode of action into the opposite of what He had determined under the condition of holy and righteous conduct of men; for he is turned back from following Me and hath not performed My commandments. Pride and self-will, in the consciousness of his own power in Israel, had caused Saul to disregard the divine charge. And it grieved Samuel, it hurt him bitterly to find that Saul had turned away from the Lord, it kindled a holy anger in his heart; and he cried unto the Lord all night, probably to obtain for Saul forgiveness for his disobedience.