13. As a father is compassionate towards his children, The Psalmist not only explains by a comparison what he has already stated, but he at the same time assigns the cause why God so graciously forgives us, which is, because he is a father. It is then in consequence of God's having 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 man has been adopted on the ground 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. That God's fatherly goodness may not be perverted as an encouragement to sin, David again repeats that God is thus favorable 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 here treated 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.

14. For he knoweth. David here annihilates all the worth which men would arrogate to themselves, and asserts that it is the consideration of our misery, and that alone, which moves God to exercise patience towards us. This again we ought carefully to mark, not only for the purpose of subduing the pride of our flesh, but also that a sense of our unworthiness may not prevent us from trusting in God. The more wretched and despicable our condition is, the more inclined is God to show mercy, for the remembrance that we are clay and dust is enough to incite him to do us good.

To the same purpose is the comparison immediately following, (verse 15,) that all the excellency of man withers away like a fading flower at the first blast of the wind. Man is indeed improperly said to flourish. But as it might be alleged that he is, nevertheless, distinguished by some endowment or other, David grants that he flourishes like the grass, instead of saying, as he might justly have done, that he is a vapor or shadow, or a thing of nought. Although, as long as we live in this world, we are adorned with natural gifts, and, to say nothing of other things, "live, and move, and have our being in God," (Acts 17:28;) yet as we have nothing except what is dependent on the will of another, and which may be taken from us every hour, our life is only a show or phantom that passes away. The subject here treated, is properly the brevity of life, to which God has a regard in so mercifully pardoning us, as it is said in another psalm: "He remembered that they were but flesh, a wind that passeth away, and cometh not again," (Psalm 78:39.) If it is asked why David, making no mention of the soul, which yet is the principal part of man, declares us to be dust and clay? I answer, that it is enough to induce God mercifully to sustain us, when he sees that nothing surpasses our life in frailty. And although the soul, after it has departed from the prison of the body, remains alive, yet its doing so does not arise from any inherent power of its own. Were God to withdraw his grace, the soul would be nothing more than a puff or blast, even as the body is dust; and thus there would doubtless be found in the whole man nothing but mere vanity.