But David said to Abishai, "Do not destroy him; for who can stretch out his hand against the LORD's anointed, and be guiltless?"
1 Samuel 26:9
Surrounding context
26:8 Then Abishai said to David, "God has delivered your enemy into your hand this day. Now therefore, please, let me strike him at once with the spear, right to the earth; and I will not have to strike him a second time!"
26:9 But David said to Abishai, "Do not destroy him; for who can stretch out his hand against the LORD's anointed, and be guiltless?"
26:10 David said furthermore, "As the LORD lives, the LORD shall strike him, or his day shall come to die, or he shall go out to battle and perish.