John Calvin Commentary Psalms 18:25

"With the merciful thou wilt show thyself merciful; With the perfect man thou wilt show thyself perfect;" — Psalms 18:25 (ASV)

With the merciful, etc. David here pursues the same subject. In considering the grace of God by which he had been delivered, he brings it forward as a proof of his integrity, and thus triumphs over the unfounded and disgraceful slanders of his enemies. Hypocrites, I confess, are also accustomed to act in the same way; for prosperity and the success of their affairs so elates them that they are not ashamed proudly to boast not only against men, but even against God.

However, when such people openly mock God, who by his patience invites them to repentance, their wicked and unhappy presumption has no resemblance to the boasting by which we see David encouraging himself here. He does not abuse the forbearance and mercy of God by excusing or putting a deceptive gloss over his sins because God bears with them. Instead, having experienced God's mercy towards him beyond doubt through the abundant help he had received from God, he justly viewed these acts as clear testimonies of divine favor towards him.

And we should carefully observe this difference between the wicked and the faithful: namely, that the former, intoxicated with prosperity, unblushingly boast of being acceptable to God, even while they disregard him and instead sacrifice to Fortune, making it their god. The latter, however, in their prosperity magnify the grace of God, from the deep sense of his grace with which their consciences are affected. Thus David here boasts that God had helped him because of the justice of his cause. For we must understand the words in this way:

1. First, we must adapt the words to the context of the entire passage and view them as implying that God, in so often delivering an innocent man from death when it was near him, showed indeed that he is merciful towards the merciful, and pure towards the pure.
2. Second, we must view the words as teaching the general doctrine that God never disappoints his servants but always, in the end, deals graciously with them, provided they wait for his aid with meekness and patience.

To this effect, Jacob said in Genesis 30:33,

God will make my righteousness to return upon me.

The point of the passage is that the people of God should cherish good hope and encourage themselves to live uprightly and with integrity, since every man shall reap the fruit of his own righteousness.

The last clause of the 26th verse, where it is said, With the perverse you will show yourself perverse, seems to convey a somewhat strange meaning, but it does not imply anything absurd. Indeed, it is not without good reason that the Holy Spirit uses this manner of speaking, for he intends by this to awaken hypocrites and the utter despisers of God, who lull themselves asleep in their vices without any fear of danger.

We see how such people, when Scripture proclaims the severe and dreadful judgments of God, and when God himself also denounces terrible vengeance, ignore all these things without troubling themselves about them. Accordingly, this brutish and, so to speak, monstrous stupidity that we see in humanity compels God to devise new ways of speaking and, so to speak, to present himself in a different character.

There is a similar sentence in Leviticus 26:21-24, where God says, "And if you walk contrary to me [or perversely with me], then I will also walk contrary to you [or perversely or roughly, or at random against you];" as if he had said that their obstinacy and stubbornness would make him, on his part, forget his accustomed forbearance and gentleness, and act recklessly or at random against them.

We see, then, what the stubborn ultimately gain by their obstinacy: God becomes even more resolute to shatter them. If they are like stone, he makes them feel that he possesses the hardness of iron. Another reason we may suggest for this manner of speaking is that the Holy Spirit, in addressing his discourse to the wicked, commonly speaks according to their own perception.

When God thunders against them with full force, the blind terrors that seize them cause them to transform him into a character different from his real one, since they imagine his character to consist of nothing but barbarity, cruelty, and ferocity. We now see the reason why David does not simply attribute to God the name and office of judge, but introduces him as armed with impetuous violence for resisting and overcoming the perverse, as the common proverb says: A tough knot requires a stout wedge.