Martin Luther was certainly correct to keep his finger on Romans 1:16-17 as the place where the gates of heaven open up and adorn sinners with the grace of righteousness which grants us entrance into the everlasting kingdom of God.
However, as he progressed in his studies of the New Testament, he more and more defined the gift of δικαιοσύνη (righteousness) as not just an alien righteousness belonging to Jesus Christ alone, but also believed the Bible’s description of what it means to be justified as a forensic declaration on the basis of a legal imputation of of the Alien’s righteousness (i.e. Christ’s righteousness). For Luther, the grace of justification does not change our ontological person to make us δίκαιος (righteous), but remains alien always and forever. On the day of judgment, therefore, one will be examined to see if Christ’s righteousness is legally possessed by each person judged, and if they have that, then they enter into the Kingdom of God. Now, to dispel all misrepresentation, Luther did not believe that someone could conclude from all of this that the gift of salvation does not include the ontological transformation of the human person, nor that one could receive the gift of justification and then run off and live forever in sin without injury to his or her status of acceptance before God. In fact, Luther’s preaching and teaching emphasized very strongly the need for repentance and good works, perhaps even more than some of his Catholic contemporaries. These good works of obedience are not contributory to the large endowment of imputed righteousness, however, and this is partly where Catholics disagree with Lutherans. I do not attempt here to explain how this can be reconciled, or how it cannot be. I simply introduce the topic with the famous event of Luther and his discovery of the “righteousness of God” (Rom 1:17) as that which set him free.
According to the New Testament, then, what is this righteousness that saves us? I will give my brief answer to this question. Before I do that, however, I should make the preliminary note that this is not an exhaustive description of what the word “righteousness” means in all of Paul, but more narrowly those references that pertain to the salvation of the sinner through God’s gift of justification.
Phil 3:9-12 and Romans 8:8-11 make it clear that to be δίκαιος is referring to the status achieved in the sight of God that would commend one to his favor. To be δίκαιος is to have δικαιοσύνη. In his past, Saul would have said that his ethnic heritage, his tribal origins, his flesh arrangement in the Covenant through outward circumcision, his zeal for God’s vengeance against heretics and his observance of Torah gained him that status of bring commended before God for his favor and delight. But by the light of the gospel, Saul-turned-Paul learned that all of that was mitigated by the depravity of a deeper problem, one which makes the letter of the Law a ministry of death written on stones, namely, the fallen Adamic life-context as vitiated by the disorder of sin. It cannot be by circumcision, or even uncircumcision (i.e. both describe the whole of the fallen natural order of humanity, Jew and Gentile) .
It is by nature that we are children of wrath, sold under sin, and dead to God and his commandments. No amount of effort from this vantage point could achieve the status of gaining favor under God’s just examination. Paul learned that the real prayer is this – “who will deliver me from this body of death” (Rom 7:25)? That is what opens the door to another manner provided by God himself for becoming righteous. It is by a divine intervention through which the very anthropos (human being) is made new in the corpse of Jesus Christ. It is there, and nowhere else, that humanity can find life and righteousness. Thus, we attain to the status of righteousness through the blood atonement of our Lord in which our sins are forgiven, and by the renewal of the Holy Spirit which makes us alive unto God with a the power of a new obedience (Rom 6). Under this grace, which we can walk in good works to please our Creator. Another way to put is this: since the problem is with the fallen anthropos itself, the way in which humanity attains to the status of justice or righteousness is by putting off the old man and putting on the new man, who is Christ Jesus in us, the hope of glory. This is why Paul can curse his former “righteousness” and contrast it with that righteousness which comes from above, through faith in Jesus Christ, through which we know Christ and the power of his resurrection. It is in this sense that the righteousness of man by the law and the righteousness of God through faith is to be understood. Nothing in this entails that the gift of righteousness is wholly alien through and through, but just the opposite. We are, by this gift of righteousness, made alive to God and our wills are moved to goodness and holiness.
Indeed, it is those who receive the gift of righteousness from God who are the real circumcision, who worship God in the inwardly new heart by the Spirit, and who make no boast in the flesh.
Faith is the instrument through which fallen humanity becomes subject to the new powers of resurrection in Jesus Christ. Nowhere in the New Testament is this to be understood as a mere legal transaction of an always-alien righteousness.