1 Samuel 24:3-4

And he came to the sheepcotes by the way, where was a cave; and Saul went in to cover his feet. Now David and his men were abiding in the innermost parts of the cave. And the men of David said unto him, Behold, the day of which Jehovah said unto thee, Behold, I will deliver thine enemy into thy hand, and thou shalt do to him as it shall seem good unto thee. Then David arose, and cut off the skirt of Saul’s robe privily.