John Calvin Commentary Psalms 103:13

"Like as a father pitieth his children, So Jehovah pitieth them that fear him." — Psalms 103:13 (ASV)

As a father is compassionate towards his children, the Psalmist not only explains by a comparison what he has already stated, but he also assigns the reason why God so graciously forgives us: because He is a Father. It is, therefore, because God has freely and sovereignly adopted us as His children that He continually pardons our sins, and accordingly, we are to draw from that fountain the hope of forgiveness.

And as no one has been adopted on the basis of his own merit, it follows that sins are freely pardoned. God is compared to earthly fathers, not because He is in every respect like them, but because there is no earthly image by which His unparalleled love towards us can be better expressed.

So that God’s fatherly goodness is not perverted as an encouragement to sin, David again repeats that God is favorable in this way only to those who are His sincere worshippers. It is indeed a proof of no ordinary forbearance for God to make his sun to rise on the evil and on the good, (Matthew 5:45); but the subject treated here is the free imputation of the righteousness by which we are accounted the children of God.

Now, this righteousness is offered only to those who entirely devote themselves to so bountiful a Father and reverently submit to His word. But as our attainments in godliness in this world, whatever they may be, come far short of perfection, there remains only one pillar on which our salvation can securely rest, and that is the goodness of God.