“We are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them” (Eph. 2:10)

To declare righteousness is to speak righteousness. God speaks righteousness to man, and then he is righteous. The method is the same as in the creation in the beginning. “He spoke, and it was.”

Christ is set forth to declare God’s righteousness for the remission of sins, in order that He might be just and at the same time the justifier of him who believes in Jesus. God justifies sinners, for they are they only ones who need justification. The justice of declaring a sinner to be righteous lies in the fact that he is actually made righteous. Whatever God declares to be so, is so. And then he is made righteous by the life of God given him in Christ.

The sin is against God, and if He is willing to forgive it, He has the right to do so. No unbeliever would deny the right of a man to overlook a trespass against him. But God does not simply overlook the trespass; He gives His life as a forfeit. Thus He upholds the majesty of the law, and is just in declaring that man righteous who was before a sinner. Sin is remitted- sent away- from the sinner, because sin and righteousness cannot exist together, and God puts His own righteous life into the believer. So God is merciful in His justice, and just in His mercy.

This act of mercy on the part of God is eminently just, because in the first place the sin is against God, and He has a right to pass by offenses against Him. Further, it is just, because He gives His own life as an atonement for the sin, so that the majesty of the law is not only maintained, but is magnified. God is just and the justifier of him who believes in Jesus. All righteousness is from Him alone.

Righteousness is the free gift of God to everyone who believes. True faith has Christ alone as its object, and it brings Christ’s life actually into the heart; and therefore it must bring righteousness.

Waggoner, Waggoner on Romans, pp. 73,74