John Calvin Commentary Psalms 36:10

"Oh continue thy lovingkindness unto them that know thee, And thy righteousness to the upright in heart." — Psalms 36:10 (ASV)

Prolong thy mercy to them that know thee. David now sets himself to pray. And first, he asks in general that God would continue his mercy to all the godly, and then he pleads particularly on his own behalf, imploring the help of God against his enemies. Those who affirm that God is here said to prolong or extend his mercy because it is exalted above the heavens indulge in a style of speaking too childish.

When David spoke of it in such terms in a preceding verse, his intention was not, as I have already said, to represent the mercy of God as confined to heaven, but simply to declare that it was diffused throughout the world; and here, what he desires is just this: that God would continue to manifest, even to the end, his mercy towards his people.

With the mercy of God he connects his righteousness, combining them as cause and effect. We have already said in another place that the righteousness of God is manifested in his undertaking the defense of his own people: vindicating their innocence, avenging their wrongs, restraining their enemies, and proving himself faithful in preserving their welfare and happiness against all who attack them.

Now, since God does all this for them freely, David, with good reason, particularly mentions his goodness and places it first, so that we may learn to depend entirely upon his favor.

We should also observe the terms he uses to describe true believers: first, he says that they know God; and secondly, that they are upright in heart.

We learn from this that true godliness springs from the knowledge of God, and also that the light of faith must necessarily dispose us to uprightness of heart. At the same time, we should always bear in mind that we only know God rightly when we give him the honor he deserves; that is, when we place entire confidence in him.