Romans 2:17

This is not to be read as a question, as some people think, but rather as a statement, as if to say: "Not as a true Jew, albeit in secret, but merely claiming to be one and making false pretenses."

If a Jew boasts in God in the manner called for by grace, which is given not according to the merits of works but freely, his praise would be of God and not of men.… But they thought that they had fulfilled this law of God by their own righteousness, even though they were transgressors of it. And so for them it worked wrath as sin multiplied, committed by those who knew what sin was. Those who did what the law commanded without the help of the Spirit of grace did it through fear of punishment and not out of love for righteousness.

For they become ridiculous even to the Gentiles themselves when, following the letter of the Law, they say: "Do not touch, do not taste, do not handle: all of which things are unto corruption according to the commandments and doctrines of men." But these things the Apostle indeed says to him who is a Jew in name, not in deed; yet they can pertain also to every man in whom there is only the name of religion and piety, while works, and knowledge, and faith are lacking. And therefore we ought to examine these matters with greater care in ourselves than in those who do not come to faith in Christ, lest any of us who through faith in Christ and through the circumcision given in baptism has been made a true Jew, and rests in the law of Christ, and boasts also that, having driven off the error of idols, he has come to know God and that His will has become known to him (for he knows how to prove what is good, and well-pleasing, and perfect, and has advanced so far that he is even a leader and teacher of the Church for enlightening those who are blind in knowledge, and for instructing the little ones in Christ) — lest, I say, such a man be willing indeed to teach others quite strictly, and to demand from those whom he instructs the highest discipline of chastity, while he himself is driven by the vice of intemperance and of covetousness, and sometimes even burns with the flames of hidden lust. To a man of this sort, then, this apostolic word is fittingly applied, saying to him: "You who teach another, do you not teach yourself? You who preach that a man should not steal, do you steal? […]

"Behold, thou art called a Jew, and restest in the Law, and makest thy boast of God, and knowest His will, and approvest the things that are more excellent, being instructed out of the Law." After saying that the Gentile wanteth nothing appertaining to salvation if he be a doer of the Law, and after making that wonderful comparison, he goes on to set down the glories of the Jews, owing to which they thought scorn of the Gentiles: and first the very name itself, which was of great majesty, as the name Christian is now. For even then the distinction which the appellation made was great. And so he begins from this, and see how he takes it down. For he does not say, Behold, thou art a Jew, but "art called" so, "and makest thy boast in God;" that is, as being loved by Him, and honored above all other men. And here he seems to me to be gently mocking their unreasonableness, and great madness after glory, because they misused this gift not to their own salvation, but to set themselves up against the rest of mankind, and to despise them. "And knowest His will, and approvest the things that are more excellent." Indeed this is a disadvantage, if without working: yet still it seemed to be an advantage, and so he states it with accuracy. For he does not say, thou doest, but knowest; and approvest, not followest and doest.

The beneficent action of the law, the apostle showed in the passage relating to the Jews, writing thus: "Behold, thou art called a Jew and restest in the law, and makest thy boast in God, and knowest the will of God, and approvest the things that are more excellent, being instructed out of the law, and art confident that thou thyself art a guide of the blind, a light of them who are in darkness, an instructor of the foolish, a teacher of babes, who hast the form of knowledge and of truth in the law." For it is admitted that such is the power of the law, although those whose conduct is not according to the law, make a false pretence, as if they lived in the law.