Having established the great truth that God required real moral goodness, he considers the position of the Jews. Could they not plead special divine favour? Was there no advantage in Judaism? Surely there was, especially in that they possessed the oracles of God. The ways of God were full of blessing in themselves, although that did not change the immutable truths of His nature. And if many among them had been unbelieving, this did not alter the faithfulness of God; and the fact that the unbelief of many did but the more demonstrate the faithfulness of God, who remained the same whatever they might be, took nothing from the claims of righteousness. Unbelievers should be punished according to what they were; it would but magnify the unfailing faithfulness of God, which never failed, however unavailing it might be for the mass of the nation. Otherwise He could judge no one, not even the world (which the Jew was willing to see judged); for the condition of the world also enhanced and put in evidence the faithfulness of God towards His people. If then the Jew had advantages, was he therefore better? In no wise: all were shut up under sin, whether Jew or Gentile, as God had already declared. 
The apostle now cites the Old Testament to prove this with regard to the Jews, who did not deny it with regard to the Gentiles which he had already also shewn. The law, says he, belongs to you. You boast that it refers to you exclusively. Be it so: hear then what it says of the people, of yourselves. It speaks to you, as you acknowledge. There is not then one righteous man among you on whom God can look down from heaven. He quotes Psalm 14:2, 3; Isaiah 59:7, 8, to set forth the judgment pronounced on them by those oracles of which they boasted. Thus every mouth was shut, and all the world guilty before God. Therefore it is that no flesh can be justified before God by the law; for if the world in the midst of darkness wallowed in sin, by means of the law sin was known.
But now, without law, apart from all law, a righteousness that is of God has been manifested, the law and the prophets bearing witness to it.
Hence then we find not only the condition of the Gentiles and of the Jews set forth, together with the great immutable principles of good and evil, whatever might be the dealings of God, but the effect of the law itself, and that which was introduced by Christianity as regarded righteousness, altogether outside the law, although the law and the prophets bore witness to it. In a word, the eternal truth as to sin and as to the responsibility of man, the effect of the law, the connection of the Old Testament with Christianity, the true character of the latter in that which relates to righteousness (namely, that it is a thing entirely new and independent), the righteousness of God Himself-the whole question between man and God, with regard to sin and righteousness, is settled, as to its foundation, in these few words. The manner of its accomplishment is now to be treated of.  It is the righteousness of God by faith in Jesus Christ. Man has not accomplished it, man has not procured it. It is of God, it is His righteousness; by believing in Jesus Christ participation in it is obtained. Had it been a human righteousness, it would have been by the law which is the rule of that righteousness-a law given to the Jews only. But being the righteousness of God Himself, it had reference to all; its range embraced not the one more than the other. It was the righteousness of God “unto all.” A Jew was not more in relation with the righteousness of God than a Gentile. It was in fact universal in its aspect and in its applicability. A righteousness of God for man, because no man had any for God, it was applied to all those who believe in Jesus. Wherever there was faith, there it was applied. The believer possessed it. It was towards all, and upon all those who believed in Jesus. For there was no difference: all had sinned, and outside the glory of God,  deprived of that glory, were justified freely by His grace, through the redemption that is in Christ Jesus. Whether a Jew or a Gentile, it was a sinful man: the righteousness was the righteousness of God; the goodness of God was that which bestowed it, redemption in Christ Jesus the divine means of having part in it.  Before the accomplishment of this redemption, God, in view of it, had in patience borne with the faithful, and His righteousness in forgiving them was now clearly manifested. But, further, the righteousness itself was manifested: we come to Christ as a propitiatory that God has set forth before men, and we find on it the blood which gives us free access to God in righteousness,-God whose glory is satisfied in the work that Christ Jesus has accomplished, His blood upon the mercy-seat bearing witness thereof. It is no longer “forbearance”-righteousness is manifested, so that God is seen to be righteous and just in justifying him who is of faith in Jesus. Where then is boasting? For the Jews boasted much in reference to the Gentiles-self-righteousness always boasts: it is not a law of works that can shut it out. Man justifying himself by his works would have something to boast in. It is this law of faith, this divine principle on which we are placed, which shuts it out: for it is by the work of another, without works of law, that we through grace have part in divine righteousness, having none of our own.
 -the God of the Jews only? No, He is also the God of the Gentiles. And how? In grace: in that it is one God who justifies the Jews (who seek after righteousness) on the principle of faith, and-since justification is on the principle of faith-the believing Gentiles also by faith. Men are justified by faith; the believing Gentile then is justified. With regard to the Jew, it is the principle which is established (for they were seeking the righteousness). With regard to the Gentile, since faith existed in the case supposed, he was justified, for justification was on that principle.
Is it then that faith overturned the authority of law? By no means. It established completely the authority of law; but it made man participate in divine righteousness, while acknowledging his just and total condemnation by the law when under it-a condemnation which made another righteousness necessary, since according to the law man had none-had none of his own. The law demanded righteousness, but it shewed sin was there. If righteousness which it demanded had not been necessary, when it failed to produce it in man, there was no need of another. Now faith affirmed this need and the validity of man’s condemnation under law, by making the believer participate in this other righteousness, which is that of God. That which the law demanded it did not give; and even, because it demanded it, man failed to produce it. To have given it would have effaced the obligation. God acts in grace, when the obligation of the law is fully maintained in condemnation. He gives righteousness, because it must be had. He does not efface the obligation of the law, according to which man is totally condemned;  but, while recognising and affirming the justice of that condemnation, He glorifies Himself in grace by granting a divine righteousness to man, when he had no human righteousness to present before God in connection with the obligations imposed on him by the law. Nothing ever put divine sanction on the law like the death of Christ, who bore its curse, but did not leave us under it. Faith does not then annul law; it fully establishes its authority. It shews man righteously condemned under it, and maintains the authority of the law in that condemnation, for it holds all who are under it to be under the curse.  The reader will remark that what is distinctly set forth to the end of this third chapter is the blood of Christ as applying itself to the sins of the old man, hence making forgiving a righteous thing, and the believer clear from sins, because cleared by Christ’s blood. This met all the guilt of the old man.
We now enter on another aspect of that which justifies, but still proves sins; not yet, however, putting us in a new place-that of resurrection, in connection with, and consequent on, this.
 Note here a very important principle, that there are positive advantages of position, where there is no intrinsic change. Compare chapter 11:17, and 1 Corinthians 10.
 Chapter 3:21 reverts in fact to chapter 1:17; what comes between is the demonstration of the ground of chapter 1:18, which made the righteousness of verse 17 imperatively necessary.
 Remark here how, God being revealed, sin is measured by the glory of God. We are so used to read this that we overlook its force. How strange to say, “and come short of the glory of God!” Man might say, Why, of course we have; but, morally speaking, this has been revealed, and if one cannot stand before it, according to it, we cannot subsist before God at all. Of course it is not of His essential glory-all creatures are short of that, of course-but of that which was fitting for, according to, could stand in, His presence. If we cannot stand there, fitly “walk in the light as God is in the light,” we cannot be with God at all. There is no veil now.
 To shew how complete is this instruction of Paul’s, I give here a summary of its elements. In itself it is the righteousness of God, without law, the law and the prophets bearing witness to it: as to its application, the righteousness of God by faith in Christ Jesus unto all, and upon all them that believe. Christ is proposed as the propitiatory by faith in His blood, to shew forth this righteousness by the remission of past sins (of the Abrahams, etc.) according to the forbearance of God; but to shew it forth in the present time, in order that He may be just, and justify those who believe in Jesus.
 See here again how God is brought out in Himself. Compare Matthew 15:19-28.
 The law is the perfect rule of right and wrong for every child of Adam in itself, though only given to the Jews. But it was not arbitrary. It took up all the relationships in which men stood, gave a perfect rule as to them, and the sanction of God’s authority to them, with a penal sanction. But now we have something much higher, not what man ought to be, but God Himself glorified.
 Hence those who put Christians under law do not maintain its authority; for they hold them exempt from its curse, though they break it.