1 Samuel 24:20-22

24:20 Now look, I realize that you will in fact be king and that the kingdom of Israel will be established in your hand. 24:21 So now swear to me in the Lord’s name that you will not kill my descendants after me or destroy my name from the house of my father.”

24:22 David promised Saul this on oath. Then Saul went to his house, and David and his men went up to the stronghold.