1 Samuel 24:17-21

17And he said to David, Thou art more righteous than I: for thou hast rewarded me with good, though I have rewarded thee with evil. 18And thou hast showed this day how thou hast dealt with me: forasmuch as when the LORD had delivered me into thy hand, thou didst not kill me.1 19For if a man findeth his enemy, will he let him go away well? therefore the LORD reward thee with good for what thou hast done to me this day. 20And now, behold, I know well that thou shalt surely be king, and that the kingdom of Israel shall be established in thy hand. 21Swear now therefore to me by the LORD, that thou wilt not cut off my seed after me, and that thou wilt not destroy my name out of my father’s house.