1 Samuel 26:15-17

15 And David said to Abner, Are not thou a valiant man? And who is like to thee in Israel? Why then have thou not kept watch over thy lord the king? For there came one of the people in to destroy the king thy lord.

16 This thing is not good that thou have done. As LORD lives, ye are worthy to die because ye have not kept watch over your lord, LORD's anointed. And now see where the king's spear is, and the cruse of water that was at his head.

17 And Saul knew David's voice, and said, Is this thy voice, my son David? And David said, It is my voice, my lord, O king.