Rom 3:20

“How, then, is the law still said to be not good by certain heresies that clamorously appeal to the apostle, who says, "For by the law is the knowledge of sin?" To whom we say, The law did not cause, but showed sin. For, enjoining what is to be done, it reprehended what ought not to be done. And it is the part of the good to teach what is salutary, and to point out what is deleterious; and to counsel the practice of the one, and to command to shun the other. Now the apostle, whom they do not comprehend, said that by the law the knowledge of sin was manifested, not that from it it derived its existence. And how can the law be not good, which trains, which is given as the instructor to Christ, that being corrected by fear, in the way of discipline, in order to the attainment of the perfection which is by Christ?”

“Well, the body tills the ground, and hastes to it; but the soul is raised to God: trained in the true philosophy, it speeds to its kindred above, turning away from the lusts of the body, and besides these, from toil and fear, although we have shown that patience and fear belong to the good man. For if "by the law is the knowledge of sin," as those allege who disparage the law, and "till the law sin was in the world;" yet "without the law sin was dead," we oppose them. For when you take away the cause of fear, sin, you have taken away fear; and much more, punishment, when you have taken away that which gives rise to lust.”

“Let us see in what way knowledge of sin comes through the law. It comes insofar as we learn through the law what to do and what not to do, what is sin and what is not sin. It is not, as the heretics claim, that God's law is a bad root or a bad tree through which a knowledge of sin comes. Rather the law is like a medicine through which we perceive the true nature of our disease.… The medicine itself is good, not least because it enables us to isolate the disease and seek to cure it.”

“"For by the Law is the knowledge of sin." He springs upon the Law again, with forbearance however (for what he says is not an accusation of it, but of the listlessness of the Jews). Yet nevertheless he has been earnest here with a view (as he was going to introduce his discourse about faith) to show its utter feebleness. For if thou boastest in the Law, he means, it puts thee to the greater shame: it solemnly parades forth your sins before you. Only he does not word it in this harsh way, but again in a subdued tone; "For by the Law is the knowledge of sin." And so the punishment is greater, but that because of the Jew. For the Law accomplished the disclosure of sin to you, but it was your duty then to flee it. Since then you have not fled you have pulled the punishment more sorely on yourself, and the good deed of the Law has been made to you a supply of greater vengeance. Now then having added to their fear, he next brings in the things of grace, as having brought them to a strong desire of the remission of their sins...”

“By the works of the law Paul means circumcision, the sabbath and the other ceremonies, which had less to do with righteousness than with carnal pleasure. Through the law comes neither forgiveness nor sin itself but rather recognition of sin. Through the law a man realizes what sin is, either because the natural law had been forgotten or because before the written law was given, the lesser sins [i.e., the sins which were more harmful to oneself than others, like lust, drunkenness, etc.] were not recognized as sins.”

“Some think that statements like this are an attack on the law. But they must be read very carefully, so that neither is the law condemned by the apostle nor is free will taken away from man. Therefore, let us distinguish the following four states of human existence: before the law, under the law, under grace and at rest. Before the law we follow the lust of the flesh. Under the law we are dragged along by it. Under grace we neither follow it nor are dragged along by it. At rest there is no lust of the flesh.Prior to being addressed by the law, we do not struggle, because not only do we lust and sin, we even approve of sinning. Under the law we struggle but are defeated. We admit that what we do is evil and that we do not want to do it, but because there is as yet no grace, we are defeated. In this state we discover how far down we lie, and when we want to rise up and yet we fall, we are all the more gravely afflicted. The law is good because it forbids what ought to be forbidden and requires what ought to be required. But when anyone thinks he can fulfill the law in his own strength and not through the grace of his Deliverer, this presumption does him no good but rather harms him so much that he is seized by an even stronger desire to sin and by his sins ends up as a transgressor. So when the man who has fallen realizes that he cannot raise himself, let him cry to his Deliverer for help. Then comes grace, which can pardon previous sins, give aid to the struggling, supplement justice with love and take away fear. When this takes place, although fleshly desires continue to fight against our spirit in this life and try to lead us into sin, yet our spirit does not give in to these desires because it is rooted in the grace and love of God and ceases to sin. For we do not sin by having these perverse desires but by giving in to them. These desires arise from the mortality of the flesh, which we inherit from the first sin of the first man, which is why we are born carnal. Nor will they cease until, by the resurrection of the body, we shall obtain the transformation which has been promised to us. Then we shall be in the fourth state, where there is perfect peace. Perfect peace is the state in which nothing will resist us because we do not resist God. Free will existed perfectly in the first man, but in us, prior to grace, there is no free will which would enable us not to sin but only enough that we do not want to sin. But grace makes it possible not only for us to want to do what is right but actually to do it not in our own strength but by the help of our Deliverer, who at the resurrection will give us that perfect peace which is the consequence of good will.”

“The purpose of the law, says Paul, is to give us a knowledge of sin not only to forbid the doing of things which are inappropriate but also to punish those who do such things.”

“The Apostle does not mean that they sinned so that their mouths would be stopped; but they were reproved by the prophets so that they would not present their sins as sins of ignorance and boast. And not only the Jews, but "the whole world becomes guilty before God," that is, condemned, lacking boldness, not justified by their own works, but in need of outside help, that is, the grace of Christ. Why then do you, O Jew, boast in the law, when you are equally guilty along with the rest of the world as one not justified by the works of the law?”

“There is a charity in act, and there is one in affection. And concerning that which is of work, I think the law was given to men and a commandment was formed: for who so possesses it in affection as it is commanded? Therefore the one is commanded for merit, the other is given as a reward. We do not deny that divine grace can grant its beginning indeed, and its progress, to be experienced even in the present life; but its consummation we firmly reserve for future happiness. How then was it right to command what was in no way to be fulfilled? Or if it pleases you more that the commandment was given concerning affectual charity, I do not contend about that, provided that you too agree with me that it could in no way be fulfilled in this life by any man, or could have been. For who would dare arrogate to himself that which Paul himself confesses he has not comprehended? (Phil 3:13.) Nor was the weight of the precept, exceeding the powers of men, hidden from the teacher; but he judged it useful that they be reminded of their own insufficiency from this very thing, and that they might know clearly toward what end of righteousness they ought to strive with their powers. Therefore by commanding impossible things he did not make men transgressors, but humble, so that every mouth may be stopped, and the whole world may be made subject to God; because by the works of the law no flesh shall be justified before him (Rom 3:19-20). For receiving the commandment, and feeling our transgression, we shall cry out to heaven, and God will have mercy on us: and we shall know in that day, that not by works of righteousness which we have done, but according to his mercy he saved us (Titus 3:5).”

“Then when he says because by the works of the law, he assigns the reason for these words: first, he assigns the reason; second, he explains it, at for by the law. First, therefore, he says: the reason there is not any man just is that no flesh shall be justified before him, i.e., according to his judgment, by the works of the law; because, as is stated in Galatians: if justification were through the law, then Christ died to no purpose (Gal 2:21), and in Titus: not because of deeds done by us in justice, but in virtue of his own mercy he saved us (Titus 3:5). However, a work of the law is of two kinds: one is peculiar to the Mosaic law, as the observance of ceremonial precepts; the other is a work of the law of nature, because it pertains to the natural law, as you shall not kill, you shall not steal, etc. Now some take the Apostle's words as referring to the first works, namely, that the ceremonials did not confer the grace through which men are made just. But this does not seem to be the Apostle's intent, for he immediately adds: for by the law is the knowledge of sin. But it is clear that sins are made known through prohibitions contained in the moral precepts. Consequently, the Apostle intends to say that by no works of the law, even those commanded by the moral precepts, is man justified in the sense that justice would be caused in him by works, because, as he states below: and if by grace, it is not now by works (Rom 11:6). Then when he says, for by the law, he proves his statement, namely, that the works of the law do not justify. For the law is given that man might know what to do and what to avoid: he has not dealt thus with any other nation; they do not know his ordinances (Ps 147:20); the commandment is a lamp and the teaching a light and the way of life (Prov 6:23). But from the fact that man knows a sin he should avoid as being forbidden, it does not at once follow that he avoids it (because this pertains to the nature of justice), because concupiscence subverts the judgment of reason, when it bears on a particular moral action as performable. Consequently, the law is not enough to make one just; another remedy is needed to suppress concupiscence.”

“Paul never says that they will not be justified before God because they have not kept the law of righteousness in the commandments but because they have refused to believe the sacrament of the mystery of God, which is in Christ. For God has declared that they should be justified by Christ and not by the law, which may justify for a time, but not before God. Therefore those who keep the law are justified in time, not before God, because faith, by which they are justified before God, is not in them. For faith is greater than the law. The law pertains to us but faith pertains to God. The law has a temporary righteousness, but faith has an eternal one. When Paul says "all flesh" he means every human being … but when he says "in the flesh" he means those who are bound by sin. For just as righteousness makes them spiritual, so also sins make them carnal, and they take the name from the deed.By faith the law is abolished, and faith then follows. What then is this law through which he says that sin is made known? Made known how? It is evident that long before Moses the patriarchs were not ignorant of sin. Joseph was thrown into prison, albeit by the wickedness of others, and both the butler and the baker of Pharaoh were in prison because of their sins. In what way then did sin lie dormant? In fact, the law has three aspects to it. The first concerns the mystery of God's divinity. The second is what is fitting according to natural law, which forbids sin. And the third is the deeds of the law, e. g., sabbaths, new moons, circumcision, etc. Here Paul refers to the natural law which was partly reformed and partly confirmed by Moses, which made sin known to all who were bound in wickedness.… The law shows the coming judgment of God and that no sinner will escape punishment, in case someone who has escaped for a time thinks that the law is an illusion. This is what the law shows: that sin will be dealt with by God.”