Matthew Henry on 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.