What is the meaning of Romans 4:6-8?

6 Even as David also describeth the blessedness of the man, unto whom God imputeth righteousness without works, 7 Saying, Blessed are they whose iniquities are forgiven, and whose sins are covered. 8 Blessed is the man to whom the Lord will not impute sin. (Romans 4:6-8 KJV)

William Burkitt’s Commentary

Observe here, That to the example of Abraham, the apostle subjoins the testimony of David, Ps 32 . who describes the blessedness of the man to whom God imputes righteousness, to wit, the righteousness of the Mediator, without any works brought before God to be justified by, saying,  Blessed is the man whose transgression is forgiven, whose sin is covered, and iniquity not imputed. Sin, in respect of the offence, is remitted; in respect of the filth or turpitude of it, is covered; in respect of the punishment, not imputed. This heap of words serves only to amplify and set forth the abundant grace of God in the act of pardoning sin.

Learn hence, 1. That to pardon sin is God’s prerogative; he forgives iniquity and covers transgression.

2. That pardon of sin is a covering of sin; not such a covering of sin, as that God cannot see it in a justified person to chastise him for it; but so covered, as not to punish him with wrath and condemnation for it.

Learn, 3. That God’s act in pardoning and covering sin, is extensive and perfect, full and final: Iniquity, transgression, and sin are forgiven, covered, and not imputed.

Learn, 4. That transcendent is the blessedness of those whose iniquity is pardoned and their transgression covered.  Blessedness, says the original, belongs to the man whose iniquity is forgiven, whose sin is covered, and to whom the Lord will not impute transgression.