Even the righteousness of God which is by faith in Jesus Christ unto all and upon all them that believe: for there is no difference:
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Ambrosiaster
AD 400
What else comes through faith in Jesus Christ except the righteousness of God which is the revelation of Christ? For it is by faith in the revelation of Jesus Christ that the gift long ago promised by God is acknowledged and received. Commentary on Paul’s Epistles.
How could Paul have promised glory, honor and peace to the good works of Gentiles apart from the grace of the gospel? Because there otherwise is no acceptance of persons with God. And because it is not the hearers but the doers of the law who are justified, he argues that all, whether Jew or Gentile, shall alike have salvation in the gospel.
Paul says “for all” meaning first the Jews, in that it was from among them that salvation first arose, and then the Gentiles, in that from the Jews grace had abounded even to them so that now both share in it together. This grace is not given in general but only to those “who believe,” but it is common to all these without distinction. .
In order to stop anyone from asking: “How can we be saved without contributing anything at all to our salvation?” Paul shows that in fact we do contribute a great deal toward it—we supply our faith! Homilies on Romans