2 Then Saul took three thousand chosen men out of all Israel, and went to seek David and his men upon the rocks of the wild goats. 3 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. 4 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. 5 And it came to pass afterward, that David's heart smote him, because he had cut off Saul's skirt. 6 And he said unto his men, Jehovah forbid that I should do this thing unto my lord, Jehovah's anointed, to put forth my hand against him, seeing he is Jehovah'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.