1 Samuel 24:17
And he said to David, Thou art more righteous than I: for thou hast rewarded me good, whereas I have rewarded thee evil. And he said to David, Thou art more righteous than I: for thou hast rewarded me good, whereas I have rewarded thee evil.
The words were spoken after David spared Saul's life in the cave and proved it by the cut-off skirt of Saul's robe. In saying them, Saul admitted the truth of David's words that David had done him no evil and had no transgression in his hand, while Saul had hunted David's life to take it. Realizing how completely he had been in the power of the man whose life he sought, and seeing David standing before him in conscious innocence, Saul was deeply moved and with softened spirit wept.
He then confessed that David was more righteous than he, because David had rewarded him with good by sparing him, whereas Saul had rewarded David with evil by seeking to kill him. This showed that David acted righteously and returned good for evil despite Saul's opposition. David was able to act this way and stand against the established king who was determined to keep his power because he trusted God's promise of the throne.