1 Samuel 16:21-23
16:21 David came to Saul and stood before him. Saul liked him a great deal, and he became his armor bearer.
16:22 Then Saul sent word to Jesse saying, “Let David be my servant, for I really like him.”
16:23 So whenever the spirit from God would come upon Saul, David would take his lyre and play it. This would bring relief to Saul and make him feel better. Then the evil spirit would leave him alone.