1 Samuel 24:7, 10-11

So David restrained his men and did not let them kill Saul. After Saul had left the cave and gone on his way

This very day you can see with your own eyes it isn’t true. For the LORD placed you at my mercy back there in the cave. Some of my men told me to kill you, but I spared you. For I said, ‘I will never harm the king—he is the LORD’s anointed one.’ Look, my father, at what I have in my hand. It is a piece of the hem of your robe! I cut it off, but I didn’t kill you. This proves that I am not trying to harm you and that I have not sinned against you, even though you have been hunting for me to kill me.