1 Samuel 26:7-12

So David and Abishai went to the army by night. And there lay Saul sleeping within the encampment, with his spear stuck in the ground at his head, and Abner and the army lay around him. Then Abishai said to David, “God has given your enemy into your hand this day. Now please let me pin him to the earth with one stroke of the spear, and I will not strike him twice.” But David said to Abishai, “Do not destroy him, for who can put out his hand against the LORD’s anointed and be guiltless?” And David said, “As the LORD lives, the LORD will strike him, or his day will come to die, or he will go down into battle and perish. The LORD forbid that I should put out my hand against the LORD’s anointed. But take now the spear that is at his head and the jar of water, and let us go.” So David took the spear and the jar of water from Saul’s head, and they went away. No man saw it or knew it, nor did any awake, for they were all asleep, because a deep sleep from the LORD had fallen upon them.