1 Samuel 19:4-6

4Jonathan spoke well of David to Saul his father and said to him, “Let not the king do wrong to his servant David; he has not wronged you, and what he has done has benefited you greatly. 5He took his life in his hands when he killed the Philistine. The Lord won a great victory for all Israel, and you saw it and were glad. Why then would you do wrong to an innocent man like David by killing him for no reason?” 6Saul listened to Jonathan and took this oath: “As surely as the Lord lives, David will not be put to death.”