I Samuel 24:3-7

So he came to the sheepfolds by the road, where there was a cave; and Saul went in to attend to his needs. (David and his men were staying in the recesses of the cave.) Then the men of David said to him, “This is the day of which the LORD said to you, ‘Behold, I will deliver your enemy into your hand, that you may do to him as it seems good to you.’ ” And David arose and secretly cut off a corner of Saul’s robe. Now it happened afterward that David’s heart troubled him because he had cut Saul’s robe. And he said to his men, “The LORD forbid that I should do this thing to my master, the LORD’s anointed, to stretch out my hand against him, seeing he is the anointed of the LORD.” So David restrained his servants with these words, and did not allow them to rise against Saul. And Saul got up from the cave and went on his way.