2 Then Saul took three thousand chosen men out of all Israel, and went to look for David and his men in the direction of the Rocks of the Wild Goats. 3 He came to the sheepfolds beside the road, where there was a cave; and Saul went in to relieve himself. Now David and his men were sitting in the innermost parts of the cave. 4 The men of David said to him, "Here is the day of which the Lord said to you, "I will give your enemy into your hand, and you shall do to him as it seems good to you.' " Then David went and stealthily cut off a corner of Saul's cloak. 5 Afterward David was stricken to the heart because he had cut off a corner of Saul's cloak. 6 He said to his men, "The Lord forbid that I should do this thing to my lord, the Lord's anointed, to raise my hand against him; for he is the Lord's anointed."
Matthew Henry's Commentary on 1 Samuel 24:2-6
Commentary on 1 Samuel 24:1-7
(Read 1 Samuel 24:1-7)
God delivered Saul into David's hand. It was an opportunity given to David to exercise faith and patience. He had a promise of the kingdom, but no command to slay the king. He reasons strongly, both with himself and with his men, against doing Saul any hurt. Sin is a thing which it becomes us to startle at, and to resist temptations thereto. He not only would not do this bad thing himself, but he would not suffer those about him to do it. Thus he rendered good for evil, to him from whom he received evil for good; and was herein an example to all who are called Christians, not to be overcome of evil, but to overcome evil with good.