And these are contrary the one to the other: so that ye cannot do the things that ye would." Gal. 5:17b

"These two captains or leaders, the flesh and the Spirit, are one against another in your body, so that you cannot do what you would. And this verse says plainly that Paul is writing these things to the saints, that is, to the Church believing in Christ, baptized, justified, renewed, and having full forgiveness of sins. Yet he says that she has flesh rebelling against the Spirit. After the same manner he speaks of himself in the seventh chapter to the Romans: "I am carnal, sold under sin"; and again: "I see another law in my members, warring against the law of my mind," also: "O wretched man that I am!"

Here, not only the schoolmen, but also some of the old fathers are much troubled, seeking how they may excuse Paul. For it seems to them unseemly to say that that elect vessel of Christ should have sin. But we credit Paul's own words, wherein he plainly confesses that he is sold under sin, that he is led captive of sin, that he has a law in his members rebelling against him, and that in the flesh he served the law of sin. Here again they answer, that the Apostle speaks in the person of the ungodly. But the ungodly do not complain of the rebellion of their flesh, or any battle or conflict, or of the capacity and bondage of sin; for sin reigns in them. This is the complaint of Paul and of all the saints. They who have claimed that Paul and other saints had no sin have done very wickedly. For they have robbed the Church of a singular consolation; they have abolished the forgiveness of sins and made Christ of no effect.

When Paul says: "I see another law in my members," he does not deny that he has flesh, and the vices of the flesh in him. It is likely that he felt sometimes the emotions of carnal lust. But yet these emotions no doubt were well suppressed in him, and if he felt the lust of the flesh, wrath, impatience, and such like, he resisted them by the Spirit, and suffered not those emotions to bear rule in him. Therefore, let us not allow such comforting verses (wherin Paul desribes the battle of the flesh against the Spirit in his own body) to be corrupted with such foolish glosses.

But this must be our ground and anchor-hold, that Christ is our perfect righteousness." -Martin Luther

Paul does encourage us in these truthful words, (as does Luther), that we are in a war with sin, a remnant of sin that still abides in the new creation in Christ. And this war will rage, and fight, and yet we have the high ground, and victory is ours, for sin has no grip on the soul of God's child, but righteousness has now taken a grip of this new heart, and quickened spirit, where the Holy Spirit now makes His abode.
What a salvation we have here; and then yet to come, we have an eternity of no more sin, and therefore no struggle: No more flesh and Spirit war! How I look forward to that Day.