4:3. For what saith the scripture? Abraham believed God: and it was reputed to him unto justice.
Reputed, etc… By God, who reputeth nothing otherwise than it is. However, we may gather from this word, that when we are justified, our justification proceedeth from God's free grace and bounty; and not from any efficacy which any act of ours could have of its own nature, abstracting from God's grace.
4:4. Now to him that worketh, the reward is not reckoned according to grace but according to debt.
To him that worketh… Vis., as of his own fund, or by his own strength. Such a man, says the apostle, challenges his reward as a debt due to his own performances; whereas he who worketh not, that is, who presumeth not upon any works done by his own strength, but seeketh justice through faith and grace, is freely justified by God's grace.
4:5. But to him that worketh not, yet believeth in him that justifieth the ungodly, his faith is reputed to justice, according to the purpose of the grace of God.
4:6. As David also termeth the blessedness of a man to whom God reputeth justice without works:
4:7. Blessed are they whose iniquities are forgiven: and whose sins are covered.
Blessed are they whose iniquities are forgiven, and whose sins are covered… That is, blessed are those who, by doing penance, have obtained pardon and remission of their sins, and also are covered; that is, newly clothed with the habit of grace, and vested with the stole of charity.
4:8. Blessed is the man to whom the Lord hath not imputed sin.
Blessed is the man to whom the Lord hath not imputed sin… That is, blessed is the man who hath retained his baptismal innocence, that no grievous sin can be imputed to him. And, likewise, blessed is the man, who after fall into sin, hath done penance and leads a virtuous life, by frequenting the sacraments necessary for obtaining the grace to prevent a relapse, that sin is no more imputed to him.