For what the law could not do, 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:
Read Chapter 8
Ambrosiaster
AD 400
For whom was this impossible? For us of course, because we could not fulfill the commandment of the law, since we were subject to sin. For this reason God sent his Son in the likeness of sinful flesh. It is the likeness of our flesh because, although it is the same as ours is, it was sanctified in the womb and born without sin, neither did he sin in it. Therefore the womb of a virgin was chosen for the divine birth so that the divine flesh might differ from ours in its holiness. It is like ours in origin but not in sinfulness. For this reason Paul says that it is similar to our flesh, since it is of the same substance, but it did not have the same birth, because the body of the Lord was not subject to sin. The Lord’s flesh was sanctified by the Holy Spirit in order that he might be born in the same kind of body as Adam had before he sinned. By sending Christ God used sin to condemn sin…. For Christ was crucified by sin, which is Satan; hence sin sinned in the flesh of the Savior’s body...
What does sinful flesh have? Death and sin. What does the likeness of sinful flesh have? Death without sin. If it had sin it would be sinful flesh; if it did not have death it would not be the likeness of sinful flesh. As such he came—he came as Savior. He died but he vanquished death. In himself he put an end to what we feared; he took it upon himself and he vanquished it—as a mighty hunter he captured and slew the lion. Sermons for Easter Season, Homily
Here Paul clearly teaches that the precepts of the law were not fulfilled (though they should have been) because those who had the law before grace were given over to worldly goods, from which they were trying to get happiness. Nor did they have any fear except when adversity threatened these goods, and when that happened they easily withdrew from the precepts of the law. Therefore the law grew weaker as its commands went unheeded. This was not the fault of the law but came about through the flesh, because those who went after worldly goods did not love the righteousness of the law but put temporal advantage ahead of it. And so our deliverer, the Lord Jesus Christ, took on mortal flesh and came in the likeness of the flesh of sin. For death is the reward due to the flesh of sin. Of course the Lord’s death was voluntary and not something which he owed. Yet nevertheless the apostle calls the assumption of mortal flesh “sin” even if it was sinless, because when the Savior died he was made...
The reason why grace was bestowed on us through our mediator is that we who were polluted by sinful flesh might be purified by the “likeness of sinful flesh.”
He who came in the likeness of sinful flesh—not in sinful flesh—did not turn away from the remedy by which sinful flesh was ordinarily made clean…. Not from necessity but by way of example he submitted to the water of baptism, by which he wanted the people of the new law of grace to be washed from the stain of sin.
By taking upon himself flesh from a sinful substance while remaining without sin, Christ fulfilled all righteousness and condemned sin in the body. This is proved by his conflict with the spirit in the desert, for the devil is overcome not by sheer divine majesty but by a reminder of the commandment, by fasting and by a legal reply.
God forbid that Paul should ever say that Christ’s body was made of sinful flesh! Rather, it was in the likeness of sinful flesh, for although it was similar to our bodies it can scarcely be compared with them in the sense that it could not be ill with carnal uncleanness. Even from the womb Christ’s body was a holy temple, and no one is afraid to state that in so far as it was flesh, when it attained the age of reason it behaved in the way flesh normally does. Nevertheless, because the Word which sanctifies all things dwelt in his body, the potential for sin was condemned so that the fruit of this blessing might come across into us as well. For we have been transformed into his likeness, not only in spirit but in body also. When Christ dwells in us by the Holy Spirit and the sacramental blessing, then the law of sin is really condemned in us. So it is truly said that what was impossible for the law, which had been weakened by the flesh, became possible through Christ, who condemned and...
Because God has done what the law could not do, we reject Jewish customs on the ground that they were not meant for us and that it is impossible to accommodate them to the needs of the Gentiles, while we gladly accept that the Jewish prophecies contain predictions about ourselves.
For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, not in sinful flesh, (because the Son of God could not sin) hath now done; even of sin hath condemned sin in the flesh. That is, in or by his flesh, which was offered on the cross, hath condemned the tyrant sin, as guilty of so many sins, and hath destroyed his tyranny, where the apostle speaks of sin, as it were of a certain person or tyrant. (Witham)
Again it appears as if Paul is criticizing the law, but in reality he is harmonizing it with Christ. The problem with the law was that it was too weak to accomplish what it intended. … And even the law’s weakness was not its fault but the fault of the flesh, by which he means not the substance itself but the carnal mind. Just because Paul says that Christ came “in the likeness of sinful flesh,” you must not think that his flesh was any different from ours. It was because he called it “sinful” that he added the word “likeness.” For Christ did not have sinful flesh but flesh which, though it was like ours by nature, was sinless. From this it is plain that flesh is not sinful by nature. It was not by taking on a different kind of flesh nor by changing ours into something different that Christ caused it to gain the victory over sin and death. Rather, he allowed the flesh to keep its own nature, giving it the crown of victory and after its resurrection life immortal.
If the Father “sent his Son in the likeness of sinful flesh,” it must not be said that the flesh in which he appeared was illusory…. The Son was sent in the likeness of sinful flesh in order to redeem our sinful flesh by a like substance, even a fleshly one, which bore a resemblance to sinful flesh although it was itself free from sin.
If the Father "sent His Son in the likeness of sinful flesh".
of the substance. Because he would not have added the attribute "sinful".
Now in another sentence he says that Christ was "in the likeness of sinful flesh".
; ".
sin condemned sin in the flesh ".
For they who walk according to flesh are sensible as to those things which are the flesh's, and they who (walk) according to (the) Spirit those which (are) the Spirit's."