“Here [1:16-17] for the first time we touch upon the dominating theme of the epistle. As a Jew, instructed in the Old Testament, Paul knows that salvation presupposes righteousness. On God’s side, salvation means the operation of his righteousness, which is not simply his property or attribute of being right, or righteous, but also his activity in doing right, and (as we say) seeing right done; thus his righteousness issues in his vindicating—those whom it is proper that he should vindicate. This view of God’s righteousness is brought out with special clarity in a number of passages in Isaiah and the Psalms, where righteousness appears to be almost a synonym of salvation; God manifests his righteousness by delivering his people.
On man’s side, salvation requires that he be found righteous before God; that, when the great assize is held, he secures a favorable verdict. If the verdict is guilty, punishment, not salvation, must be his fate.
Thus, before salvation can be completed, righteousness must be manifested. God, the righteous judge, must do righteous judgment in his court; and, in this court, man must secure the verdict, righteous. When defined in this way, salvation seems remote—remote in time, for the last judgment has not yet taken place, and remote as possibility, for there seems no likelihood that man will ever attain any verdict other than guilty. Paul, however, asserts that the righteousness of God (not salvation, for that remains future) is now being revealed. The very word he uses (in the present tense) confirms that he is thinking of a preliminary manifestation of that divine righteousness which, in orthodox Jewish thought, could be vindicated only at the last judgment. Paul, the Christian, is convinced that this judgment (and in some measure its consequences) has been anticipated through Jesus Christ, and that in the paradox of grace God has manifested his righteousness by establishing man’s. As a Jew, Paul had believed that man’s status of righteousness before God was to be achieved by himself, through obedience to the law. As a Christian, he had come to believe that God, gracious as Jesus had shown him to be, justified men freely on the basis not of works done in obedience to the law but of faith. This revision of fundamental conceptions was not the result of the academic manipulation of theological counters; it took place because God had sent his Messiah to suffer humiliation and death and thereby to manifest his righteousness in a way accessible to faith, the only human attitude corresponding to grace on God’s part…
It is impossible to keep [the activity of God in saving] and [a status of man resulting from God’s action, righteousness as a gift from God] separate from each other: God’s saving action consists precisely in conferring on man a state of righteousness (that is, in justifying him). Even [God’s faithfulness to the covenant implied in creation, which is an apocalyptic term describing God’s promised activity in setting his rebellious creation to rights] is also included by the paradoxical use of the present tense is being revealed. It is of course important to be as precise as possible in one’s understanding of this word—as of all others—but the divisions and subdivisions are ours, not Paul’s, and for him many thoughts were comprehended under the word righteousness, and the reader must be cautious before dismissing any of them from the consideration of any passage.” (C. K. Barrett, Romans, pp. 30-31)