And be found in him, not having my own righteousness, which is of the law, but that which is through the faith of Christ, the righteousness which is of God by faith:
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If, as he tells the Colossians, “in Christ are hidden all the treasures of wisdom and knowledge,” then everything, whatever it is, is to be reckoned of no account, so that we may attain to the height of this wisdom and knowledge. Not only sufficient but superabundant indeed is the righteousness that comes from faith. This salvation is freely given by the grace of God through the knowledge of Christ. It can hardly be said to be a gift of the law. For to know rightly the mystery of his incarnation and passion and resurrection is the perfection of life and the treasure of wisdom.
Now what does he mean, “not having my own righteousness,” when that law was not his but God’s? He can only have called it his own righteousness because, although it was from the law, he used to think that he could fulfill it without the aid of the grace that is through Christ.
I may be found in him not having my justice, which is of the law; i.e. not pretending to be justified either by my own works or by the works of the Jewish law, but by that which proceedeth from faith in Christ, and by his merits. (Witham)
St. Augustine expounds the sense thus: not that justice which is in God, or by which God is just, but that which is in man from God, and by his gifts. (lib. 3. cont. 2. ep. Pelag.)
Righteousness comes from faith, which means that it too is a gift of God. For since this righteousness belongs to God, it is an unmerited gift. And the gifts of God greatly exceed any achievements of our own zeal. .