for not the hearers of the law are righteous before God, but the doers of the law shall be declared righteous:,

It is not those that merely hear the Law read who are righteous in the sight of God, but it is those that obey the Law who will be pronounced righteous.

For it is not the hearers of the law who will be judged as having righteousness before God, but only the doers:

It is not those who hear the words of a Law that are righteous before God, but it is those who obey it that will be pronounced righteous.

Non enim Legis auditores justi sunt apud Deum, sed qui Legem faciunt justificabuntur.

For the hearers of the law, etc. This anticipates an objection which the Jews might have adduced. As they had heard that the law was the rule of righteousness, (Deuteronomy 4:1,) they gloried in the mere knowledge of it: to obviate this mistake, he declares that the hearing of the law or any knowledge of it is of no such consequence, that any one should on that account lay claim to righteousness, but that works must be produced, according to this saying, "He who will do these shall live in them." The import then of this verse is the following, -- "That if righteousness be sought from the law, the law must be fulfilled; for the righteousness of the law consists in the perfection of works." They who pervert this passage for the purpose of building up justification by works, deserve most fully to be laughed at even by children. It is therefore improper and beyond what is needful, to introduce here a long discussion on the subject, with the view of exposing so futile a sophistry: for the Apostle only urges here on the Jews what he had mentioned, the decision of the law, -- That by the law they could not be justified, except they fulfilled the law, that if they transgressed it, a curse was instantly pronounced on them. Now we do not deny but that perfect righteousness is prescribed in the law: but as all are convicted of transgression, we say that another righteousness must be sought. Still more, we can prove from this passage that no one is justified by works; for if they alone are justified by the law who fulfill the law, it follows that no one is justified; for no one can be found who can boast of having fulfilled the law. [1]

Footnotes

1 - On the expression "hearers of the law," Stuart has these remarks -- "The Apostle here speaks of hoi akroatai tou nomou, because the Jews were accustomed to hear the Scriptures read in public; but many of them did not individually possess copies of the sacred volume which they could read."

For not the hearers - The same sentiment is implied in James 1:22; Matthew 7:21, Matthew 7:24; Luke 6:47. The apostle here doubtless designed to meet an objection of the Jews; to wit, that they had the Law, that they manifested great deference for it, that they heard it read with attention, and professed a willingness to yield themselves to it. To meet this, he states a very plain and obvious principle, that this was insufficient to justify them before God, unless they rendered actual obedience.
Are just - Are justified before God, or are personally holy. Or, in other words, simply hearing the Law is not meeting all its requirements, and making people holy. If they expected to be saved by the Law, it required something more than merely to hear it. It demanded perfect obedience.
But the doers of the law - They who comply entirely with its demands; or who yield to it perfect and perpetual obedience. This was the plain and obvious demand, not only of common sense, but of the Jewish Law itself; Deuteronomy 4:1; Leviticus 18:5; compare Romans 10:9.
Shall be justified - This expression is evidently synonymous with that in Leviticus 18:5, where it is said that "he shall live in them." The meaning is, that it is a maxim or principle of the Law of God, that if a creature will keep it, and obey it entirely, he shall not be condemned, but shall be approved and live forever. This does not affirm that anyone ever has thus lived in this world, but it is an affirmation of a great general principle of law, that if a creature is justified by the Law, the obedience must be entire and perpetual. If such were the case, as there would be no ground of condemnation, man would be saved by the Law. If the Jews, therefore, expected to be saved by their Law, it must be, not by hearing the Law, nor by being called a Jew, but by perfect and unqualified obedience to all its requirements. This passage is designed, doubtless, to meet a very common and pernicious sentiment of the Jewish teachers, that all who became hearers and listeners to the Law would be saved. The inference from the passage is, that no man can be saved by his external privileges, or by an outward respectful deference to the truths and ordinances of religion.

For not the hearers of the law, etc. - It does not follow, because one people are favored with a Divine revelation, that therefore they shall be saved; while the others who have not had that revelation, shall finally perish: this is not God's procedure; where he has given a law - a Divine revelation, he requires obedience to that law; and only those who have been doers of that law - who have lived according to the light and privileges granted in that revelation, shall be justified - shall be finally acknowledged to be such as are fit for the kingdom of God.

(5) (For not the hearers of the law [are] just before God, but the doers of the law shall be (h) justified.
(5) He prevents an objection which might be made by the Jews whom the law does not excuse, but condemn, because it is not the hearing of the law that justifies, but rather the keeping of it.
(h) Will be pronounced just before God's judgment seat: which is true indeed if any one could be found that had fulfilled the law: but seeing that Abraham was not justified by the law, but by faith, it follows that no man can be justified by works.

For not the hearers of the law are just before God,.... The apostle here shows, that the Jews were justly condemned, notwithstanding their having and hearing of the law; since hearing without doing it, will never denominate persons righteous in the sight of God, however it might recommend them in the sight of men: regard seems to be had either to the first delivery of the law by Moses to the people of Israel, when he read it to them, and they hearkened to it, and promised obedience; or rather to the reading and hearing it every sabbath day; and may include a speculative knowledge of it, without a practical obedience to it; and which therefore must fall greatly short of entitling them to a justifying righteousness; since not these,
but the doers of the law, shall be justified; by whom are meant, not such who merely literally and externally fulfil the law, as they imagine; for the law is spiritual, and regards the inward as well as the outward man, and requires internal holiness, as well as external obedience; and the apostle is speaking of justification before God, who sees the heart, and not before men, who judge according to outward appearance: nor are such designed who are imperfect doers of the law; for the law requires a perfect obedience, and what is not perfect is not properly righteousness; nor does it, nor can it consider an imperfect righteousness as a perfect one; for it accuses of, pronounces guilty, curses, and condemns for every transgression of it. But such only can be intended, who are doers of it spiritually, internally, as well as externally, and that perfectly. Adam, in his state of innocence, was a perfect doer of the law; he sinning, and all his posterity in him, none of them are righteous, but all pass under a sentence of condemnation. The best of men, even believers in Christ, are not without sin in themselves; and when any of the saints are said to be perfect, it must be understood in a comparative sense, or as they are considered in Christ. There never was but one since Adam, and that is Christ, who has fulfilled, or could perfectly fulfil the law; the thing is impossible and impracticable for fallen man: hence these words must be understood either hypothetically, thus, not the hearers of the law, but if there were any perfect doers of it, they would be justified before God; or else of such persons who are considered in Christ, by whom the whole perfect righteousness of the law is fulfilled in them, and who may be reckoned as perfect doers of it in him, their substitute, surety, and representative.

For not the hearers, &c.--As touching the Jews, in whose ears the written law is continually resounding, the condemnation of as many of them as are found sinners at the last involves no difficulty; but even as respects the heathen, who are strangers to the law in its positive and written form--since they show how deeply it is engraven on their moral nature, which witnesses within them for righteousness and against iniquity, accusing or condemning them according as they violate or obey its stern dictates--their condemnation also for all the sin in which they live and die will carry its dreadful echo in their own breasts.

For not the hearers of the law are, even now, just before God, but the doers of the law shall be justified - Finally acquitted and rewarded a most sure and important truth, which respects the gentiles also, though principally the Jews. St. Paul speaks of the former, Romans 2:14, &c.; of the latter, Romans 2:17, &c. Here is therefore no parenthesis; for Romans 2:16 also depends on Romans 2:15, not on Romans 2:12.