John Calvin Commentary Psalms 103:3

"Who forgiveth all thine iniquities; Who healeth all thy diseases;" — Psalms 103:3 (ASV)

Who forgiveth all thy iniquities. He now enumerates the different kinds of divine benefits, regarding which he has told us that we are too forgetful and slothful. It is not without cause that he begins with God’s pardoning mercy, for reconciliation with him is the fountain from which all other blessings flow.

God’s goodness extends even to the ungodly; but they are, nevertheless, so far from having the enjoyment of it that they do not even taste it. The first then of all the blessings of which we have the true and substantial enjoyment is that which consists in God’s freely pardoning and blotting out our sins, and receiving us into his favor.

Indeed, the forgiveness of sins, since it is accompanied by our restoration to the favor of God, also sanctifies whatever good things he bestows on us, so that they may contribute to our welfare. The second clause is: either a repetition of the same sentiment, or it opens up a wider view of it. For the consequence of free forgiveness is that God governs us by his Spirit, mortifies the lusts of our flesh, cleanses us from our corruptions, and restores us to the healthy condition of a godly and an upright life.

Those who understand the words, who healeth all thy diseases, as referring to diseases of the body, and as implying that God, when he has forgiven our sins, also delivers us from bodily maladies, seem to attribute to them a meaning too restricted. I have no doubt that the medicine spoken of relates first to the blotting out of guilt, and secondly, to curing us of the corruptions inherent in our nature, which is accomplished by the Spirit of regeneration. If anyone adds as a third particular that God, once pacified towards us, also remits the punishment we deserve, I will not object.

Let us learn from this passage that, until the heavenly Physician helps us, we nourish within us not only many diseases, but even many deaths.