1 Samuel 26:15-16

And David said to Abner, Art not thou a valiant man? and who is like to thee in Israel? wherefore then hast thou not kept thy lord the king? for there came one of the people in to destroy the king thy lord. This thing is not good that thou hast done. As the LORD liveth, ye are worthy to die, because ye have not kept your master, the LORD's anointed. And now see where the king's spear is, and the cruse of water that was at his bolster.