Perhaps someone will say that here the apostle Paul abandons the role of the weak man, which he assumed in the preceding [verses], and talks directly about himself. For he says that he serves the law of God with his mind but the law of sin with his flesh, as if to imply that the power of sin is so great that even an apostle cannot escape it. Moreover, he also said elsewhere: “I pommel my body and subdue it, lest after preaching to others I myself should be disqualified.” But someone who takes this interpretation seems to me to be inflicting every soul with despair, because then there would be nobody who did not sin in the flesh. In other words, everyone would be serving the law of sin in the flesh. Rather, it seems to me that here Paul maintains the role he has adopted and plays the part of the weak man, whom we have already described.It appears that in this passage Paul is teaching us that the mortification of the flesh, of which he has already spoken, is not something which happens overnight but rather is a gradual process, because the force of habit is such and the attraction of sin is so great that, even though our mind may want to do what is right and has decided to serve the law of God, yet the lusts of the flesh continue to urge him to serve sin and obey its laws instead.
And he immediately adds, clearly showing from what kind of death he desired to be delivered, and who he was who delivered him, "I thank God, through Jesus Christ."
“The law of God” means both the law of Moses and the law of Christ.… A free mind which has been called back to good habits by the help of the Holy Spirit can repulse evil temptations. For it has recovered its power to resist the enemy. If it is no longer subject then Satan cannot appear uninvited. Flesh, though, has no judgment, nor is it able to discern anything, because it is brute nature. It cannot close the door to the enemy, nor can it come in and persuade the mind to do the opposite to what the mind intends.Because man consists of both soul and flesh, the part which knows serves God and the part which is mute serves the law of sin. But if man perseveres in the form in which he was created, the enemy would have no power to reach the flesh and persuade it to act against the will of the soul. But because the whole man was not restored to his pristine state by the grace of Christ the sentence pronounced on Adam remains in force, for it would be unjust to abolish a sentence which was rightly pronounced. So although the sentence remains in force, a cure has been found by the providence of God, so that the salvation which man had lost by his own fault might be given back to him.
Observe how he shows the necessity of having grace present with us, and that the well-doings herein belong alike to the Father and the Son. For if it is the Father Whom he thanks, still the Son is the cause of this thanksgiving. But when you hear him say, "Who shall deliver me from the body of this death?" do not suppose him to be accusing the flesh. For he does not say "body of sin," but "body of death:" that is, the mortal body — that which has been overcome by death, not that which gendered death. And this is no proof of the evil of the flesh, but of the marring (ἐ πηρείας], thwarting) it has undergone. As if any one who was take captive by the savages were to be said to belong to the savages, not as being a savage, but as being detained by them: so the body is said to be of death, as being held down thereby, not as producing it. Wherefore also it is not the body that he himself wishes to be delivered from, but the mortal body, hinting, as I have often said, that from its becoming subject to suffering, it also became an easy prey to sin. Why then, it may be said, the thraldom of sin being so great before the times of grace, were men punished for sinning? Because they had such commands given them as might even under sin's dominion be accomplished. For he did not draw them to the highest kind of conversation, but allowed them to enjoy wealth, and did not forbid having several wives, and to gratify anger in a just cause, and to make use of luxury within bounds. [Matthew 5:38] And so great was this condescension, that the written Law even required less than the law of nature. For the law of nature ordered one man to associate with one woman throughout. And this Christ shows in the words, "He which made them at the beginning, made them male and female." [Matthew 19:4] But the Law of Moses neither forbade the putting away of one and the taking in of another, nor prohibited the having of two at once! [Matthew 5:31] And besides this there are also many other ordinances of the Law, that one might see those who were before its day fully performing, being instructed by the law of nature. They therefore who lived under the old dispensation had no hardship done them by so moderate a system of laws being imposed upon them. But if they were not, on these terms, able to get the upper hand, the charge is against their own listlessness. Wherefore Paul gives thanks, because Christ, without any rigorousness about these things, not only demanded no account of this moderate amount, but even made us able to have a greater race set before us. And therefore he says, "I thank my God through Jesus Christ." And letting the salvation which all agreed about pass, he goes from the points he had already made good, to another further point, in which he states that it was not our former sins only that we were freed from, but we were also made invincible for the future. For "there is," he says, "now no condemnation to them which are in Christ Jesus, who walk not after the flesh." Yet he did not say it before he had first recalled to mind our former condition again in the words, "So then with the mind I myself serve the law of God, but with the flesh the law of sin."
Grace sets free the man whom the law could not free. Was Paul at this time not yet set free by the grace of God? Of course! This shows that here he is speaking of somebody else. He then reviews the main points in order to conclude his argument. In a sense the carnal person is made up of two people and is divided within himself.
Though his carnal desires still exist, the man who is renewed by grace by not giving in to sin does not serve them. With his mind he serves the law of God, even though with his flesh he serves the law of sin. Paul calls the law of sin the mortal condition which stems from the transgression of Adam, because of which we are born mortal. It is because the flesh has fallen that the lusts of the flesh entice us.
These are the words of one who is now under grace but still battling against his own lust, not so that he consents and sins but so that he experiences desires which he resists.
The grace of God through Jesus Christ our Lord will free you from the body of this death; it will deliver you from the law of death. But … this is going to take place at the resurrection, when you will possess a body in which no evil inclination remains.
[AD 253] Origen of Alexandria on Romans 7:25