Then as the fact that many fall into sin even after baptism presented a difficulty (ἀ ντέπιπτεν), he consequently hastened to meet it, and says not merely “to them that are in Christ Jesus,” but adds, “who walk not after the flesh;” so showing that all afterward comes of our listlessness. For now we have the power of walking not after the flesh, but then it was a difficult task. Then he gives another proof of it by the sequel, in the words,
Ver. 2. “For the law of the Spirit of life has made me free.”
It is the Spirit he is here calling the law of the Spirit. For as he calls sin the law of sin, so he here calls the Spirit the law of the Spirit. And yet he named that of Moses as such, where he says, “For we know that the Law is spiritual.” What then is the difference? A great and unbounded one. For that was spiritual, but this is a law of the Spirit. Now what is the distinction between this and that? The other was merely given by the Spirit, but this even furnishes those that receive it with the Spirit in large measure. Wherefore also he called it the law of life in contradistinction to that of sin, not that of Moses. For when he says, It freed me from the law of sin and death, it is not the law of Moses that he is here speaking of, since in no case does he style it the law of sin: for how could he one that he had called “just and holy” so often, and destructive of sin too? But it is that which wars against the law of the mind. For this grievous war did the grace of the Spirit put a stop to, by slaying sin, and making the contest light to us and crowning us at the outstart, and then drawing us to the struggle with abundant help. Next as it is ever his wont to turn from the Spirit to the Son and the Father, and to reckon all our estate to lean upon the Trinity, so does he here also. For after saying, “Who shall deliver me from the body of this death,” he pointed at the Father as doing this by the Son, then again at the Holy Spirit along with the Son. For the law of the Spirit of Life in Christ Jesus has made me free, he says. Then again, at the Father and the Son;
Ver. 3. “For what the Law could not do,” he says, “in that it was weak through the flesh, God sending His own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh.”
Again, he seems indeed to be disparaging the Law. But if any one attends strictly, he even highly praises it, by showing that it harmonizes with Christ, and gives preference to the same things. For he does not speak of the badness of the Law, but of “what it could not do;” and so again, “in that it was weak,” not, “in that it was mischievous, or designing.” And even weakness he does not ascribe to it, but to the flesh, as he says, “in that it was weak through the flesh,” using the word “flesh” here again not for the essence and subsistency itself, but giving its name to the more carnal sort of mind. In which way he acquits both the body and the Law of any accusation. Yet not in this way only, but by what comes next also. For supposing the Law to be of the contrary part, how was it Christ came to its assistance, and fulfilled its requisitions, and lent it a helping hand by condemning sin in the flesh? For this was what was lacking, since in the soul the Lord had condemned it long ago. What then? Is it the greater thing that the Law accomplished, but the less that the Only-Begotten did? Surely not. For it was God that was the principal doer of that also, in that He gave us the law of nature, and added the written one to it. Again, there were no use of the greater, if the lesser had not been supplied. For what good is it to know what things ought to be done, if a man does not follow it out? None, for it were but a greater condemnation. And so He that has saved the soul it is, Who has made the flesh also easy to bridle. For to teach is easy, but to show besides a way in which these things were easily done, this is the marvel. Now it was for this that the Only-Begotten came, and did not depart before He had set us free from this difficulty. But what is greater, is the method of the victory; for He took none other flesh, but this very one which was beset with troubles. So it is as if any one were to see in the street a vile woman of the baser sort being beaten, and were to say he was her son, when he was the king's, and so to get her free from those who ill treated her. And this He really did, in that He confessed that He was the Son of Man, and stood by it (i.e. the flesh), and condemned the sin. However, He did not endure to smite it besides; or rather, He smote it with the blow of His death, but in this very act it was not the smitten flesh which was condemned and perished, but the sin which had been smiting. And this is the greatest possible marvel. For if it were not in the flesh that the victory took place, it would not be so astonishing, since this the Law also wrought. But the wonder is, that it was with the flesh (μετὰ σαρκὸς) that His trophy was raised, and that what had been overthrown numberless times by sin, did itself get a glorious victory over it. For behold what strange things there were that took place! One was, that sin did not conquer the flesh; another, that sin was conquered, and conquered by it too. For it is not the same thing not to get conquered, and to conquer that which was continually overthrowing us. A third is, that it not only conquered it, but even chastised it. For by not sinning it kept from being conquered, but by dying also, He overcame and condemned it, having made the flesh, that before was so readily made a mock of by it, a plain object of fear to it. In this way then, He at once unnerved its power, and abolished the death by it introduced. For so long as it took hold of sinners, it with justice kept pressing to its end. But after finding a sinless body, when it had given it up to death, it was condemned as having acted unjustly. Do you observe, how many proofs of victory there are? The flesh not being conquered by sin, Its even conquering and condemning it, Its not condemning it barely, but condemning it as having sinned. For after having convicted it of injustice, he proceeds to condemn it, and that not by power and might barely, but even by the rules of justice. For this is what he means by saying, “for sin condemned sin in the flesh.” As if he had said that he had convicted it of great sin, and then condemned it. So you see it is sin that gets condemned everywhere, and not the flesh, for this is even crowned with honor, and has to give sentence against the other. But if he does say that it was “in the likeness” of flesh that he sent the Son, do not therefore suppose that His flesh was of a different kind. For as he called it “sinful,” this was why he put the word “likeness.” For sinful flesh it was not that Christ had, but like indeed to our sinful flesh, yet sinless, and in nature the same with us. And so even from this it is plain that by nature the flesh was not evil. For it was not by taking a different one instead of the former, nor by changing this same one in substance, that Christ caused it to regain the victory: but He let it abide in its own nature, and yet made it bind on the crown of victory over sin, and then after the victory raised it up, and made it immortal. What then, it may be said, is this to me, whether it was this flesh that these things happened in? Nay, it concerns you very much. Wherefore also he proceeds:
Ver. 4. “That the righteousness of the Law might be fulfilled in us, who walk not after the flesh.”
Source: Homilies on Romans (New Advent)