1 Samuel 26:9

After that, the opportunity to kill the enemy presented itself to him twice. Once in the cave Saul fell into David's hands unawares, and again in the tent when he was relaxed in sleep. David stood over him when he was asleep, and when he could have satisfied all his anger by murdering the one who pursued him, he did not lay a hand on him himself, and he said to the one eager for the kill, "Do not destroy." The voice which prevents destruction in the case of this man is obviously the voice of God.For this reason, just as those who produce the more notable inscriptions on stones cut the characters deeply by frequently applying the chisel with blows to the carving of the letters, so the Holy Spirit contrives, by means of continuous repetition, that this great saying may become more distinct and quite clear on the stela of our memory, so that this inscription, having been carved in us distinctly and without confusion, might be known well in the time of misfortunes. For, in my opinion, the goal of the economy of the Holy Spirit is to set forth the previous accomplishments of holy ones for guidance for the life after these accomplishments, the representation leading us forward to good which is equal and similar. For whenever the soul swells with revenge against someone who is provoking it, and the blood around the heart boils with anger against the one who has grieved the soul, then, when one has looked up at this stela which the Holy Spirit set up for David, and has read the word on it which David uttered on behalf of him who was eager for his own blood, he will not fail to calm the troubled thoughts in his soul and appease his passion by his desire to imitate the same things.

But our Saviour is so gentle that He teaches thus, "If any man wills to come after Me," and, "Whoever wills to be My disciple;" and coming to each He does not force them, but knocks at the door and says, "Open unto Me, My sister, My spouse;" and if they open to Him, He enters in, but if they delay and will not, He departs from them. For the truth is not preached with swords or with darts, nor by means of soldiers; but by persuasion and counsel.

But what great and wonderful and Christian patience is to be found in David from whom Christ descended according to the flesh! David often had the opportunity to kill King Saul, his persecutor, who was eager to destroy him. Yet when Saul was subject to him and in his power, David preferred to save his life and did not retaliate on his enemy but, on the contrary, even avenged him when he was killed. In short, many prophets have been killed, many martyrs have been honored with glorious deaths, and all have attained their heavenly crowns through the merit of patience, for a crown for sorrow and suffering cannot be obtained unless patience in sorrow and suffering precede.

For who has stretched out his hand against the Lord's anointed? etc., according to the ongoing exposition indeed demonstrates that no one is free from the crime of sacrilege, who attempts to invade the kingdom of the Jewish people, given specially to him by the …

And he gave two reasons for it:-- 1. It would be a sinful affront to God's ordinance. Saul was the Lord's anointed, king of Israel by the special appointment and nomination of the God of Israel, the power that was, and to resist him was to resist the ordinance of God, Rom. xiii.