"And he well said, "a righteousness of mine own," not that which I gained by labor and toil, but that which I found from grace. If then he who was so excellent is saved by grace, much more are you. For since it was likely they would say that the righteousness which comes from toil is the greater, he shows that it is dung in comparison with the other. For otherwise I, who was so excellent in it, would not have cast it away, and run to the other. But what is that other? That which is from the faith of God, i.e. it too is given by God. This is the righteousness of God; this is altogether a gift. And the gifts of God far exceed those worthless good deeds, which are due to our own diligence."
John Chrysostom, Homily on Philippians 3
Chrysostom does not always get his exposition of the Word of God right (cf. Walther's comments in Law & Gospel, ch 7), but when he does get it right, as here, imo he exceeds all the other Fathers in the clarity of his preaching of the Gospel.
It is salutary to contemplate what might have been if Chrysostom's grasp of the meaning of the righteousness of God had survived through the Middle Ages. As it was, scholasticism distorted the meaning of the term to mean the retributive righteousness of God by which he condemns and punishes sinners. Thus when Luther, meditating on Romans 1:17 in his monastic cell at Wittenberg, was led to realize that "the righteousness of God" was a gift that came through faith, it was as though the Gospel had been rediscovered and the gates of Heaven opened, as he himself tells us: "I was altogether born again and had entered paradise itself through open gates . . . that place in Paul was for me truly the gate to paradise."