Galatians 5:16

Every soul, then, by reason of its birth, has its nature in Adam until it is born again in Christ; moreover, it is unclean all the while that it remains without this regeneration; and because unclean, it is actively sinful, and suffuses even the flesh (by reason of their conjunction) with its own shame. Now although the flesh is sinful, and we are forbidden to walk in accordance with it, and its works are condemned as lusting against the spirit, and men on its account are censured as carnal, yet the flesh has not such ignominy on its own account. For it is not of itself that it thinks anything or feels anything for the purpose of advising or commanding sin. How should it, indeed? It is only a ministering thing, and its ministration is not like that of a servant or familiar friend, animated and human beings; but rather that of a vessel, or something of that kind: it is body, not soul. …

18. All we therefore, who believe in the Living and True God, Whose Nature, being in the highest sense good and incapable of change, neither doth any evil, nor suffers any evil, from Whom is every good, even that which admits of decrease, and Who admits not at all of decrease in His own Good, Which is Himself, when we hear the Apostle saying, “Walk in the Spirit, and perform ye not the lusts of the flesh. For the flesh lusteth against the Spirit, and the Spirit against the flesh: For these are opposed one to another, that ye do not what ye would.” Far be it from us to believe, what the madness of the Manichees believes, that there are here shown two natures or principles contrary one to another at strife, the one nature of good, the other of evil. …

20. There are therefore in us evil desires, by consenting not unto which we live not ill: there are in us lusts of sins, by obeying not which we perfect not evil, but by having them do not as yet perfect good. The Apostle shows both, that neither is good here perfected, where evil is so lusted after, nor evil here perfected, whereas such lust is not obeyed. The one forsooth he shows, where he says, “To will is present with me, but to perfect good is not;” the other, where he says, “Walk in the Spirit, and perfect not the lusts of the flesh.” For neither in the former place doth he say that to do good is not with him, but “to perfect,” nor here doth he say, Have not “lusts of the flesh,” but “perfect not.” Therefore there take place in us evil lusts, when that pleases which is not lawful; but they are not perfected, when evil lusts are restrained by the mind serving the Law of God. …

25. But, say they, how is the flesh by a certain likeness compared unto the Church? What! doth the Church lust against Christ? whereas the same Apostle said, “The Church is subject unto Christ.” Clearly the Church is subject unto Christ; because the spirit therefore lusteth against the flesh, that on every side the Church may be made subject to Christ; but the flesh lusteth against the spirit, because not as yet hath the Church received that peace which was promised perfect. And for this reason the Church is made subject unto Christ for the pledge of salvation, and the flesh lusteth against the spirit from the weakness of sickness. For neither were those other than members of the Church, unto whom he thus spake, “Walk in the spirit, and fulfill not the lusts of the flesh. …

On the words of the Gospel, John v. 31 ,“If I bear witness of myself,” etc.; and on the words of the apostle, Galatians v. 16 , “Walk by the spirit, and ye shall not fulfil the lust of the flesh. For the flesh lusteth,” etc.

6. What struggle? “But if ye bite and devour one another, take heed that ye be not consumed one of another. But I say, Walk in the Spirit.” I am quoting the words of the Apostle, which have been just read out of his Epistle. “But I say, Walk in the Spirit, and ye shall not fulfil the lusts of the flesh.” “But I say, Walk in the Spirit, and the lusts of the flesh,” he did not say, “Ye shall not have;” nor did he say, “Ye shall not do;” but, “Ye shall not fulfil.” Now what this is, with the Lord’s assistance, I will declare as I shall be able; give attention, that ye may understand, if ye are walking in the Spirit. “But I say, Walk in the Spirit, and ye shall not fulfil the lusts of the flesh.” Let him follow on; if haply anything, as this which is here obscure, may be understood more easily by the sequel of his words. …

Ver. 16 . “But I say, Walk by the Spirit, and ye shall not fulfil the lust of the flesh.”

38. Something else I will say to my friends who marry and after long chastity and continence begin to burn and are as wanton as the brutes: “Are ye so foolish? having begun in the Spirit, are ye now perfected in the flesh? Did ye suffer so many things in vain?” If the Apostle in the case of some persons loosens the cords of continence, and lets them have a slack rein, he does so on account of the infirmity of the flesh. This is the enemy he has in view when he once more says: “Walk by the Spirit, and ye shall not fulfill the lust of the flesh. For the flesh lusteth against the Spirit, and the Spirit against the flesh.” It is unnecessary now to speak of the works of the flesh: it would be tedious, and he who chooses can easily gather them from the letter of the Apostle. …

3. The apostle Peter, to whom it was said,“He that is bathed needeth not to wash again,” and“Thou art Peter, and upon this rock I will build my Church,” through fear of a maid-servant denied Him. Our Lord himself says, “Simon, Simon, behold Satan asked to have you, that he might sift you as wheat. But I made supplication for thee, that thy faith fail not.” And in the same place, “Watch and pray, that ye enter not into temptation: the spirit indeed is willing, but the flesh is weak.” If you reply that this was said before the Passion, we certainly say after the Passion, in the Lord’s prayer, “Forgive us our debts, as we also forgive our debtors; and lead us not into temptation, but deliver us from the evil one.” If we do not sin after baptism, why do we ask that we may be forgiven our sins, which were already forgiven in baptism? Why do we pray that we may not enter into temptation, and t …

54. What of the laboriousness of his teaching? The manifold character of his ministry? His loving kindness? And on the other hand his strictness? And the combination and blending of the two; in such wise that his gentleness should not enervate, nor his severity exasperate? He gives laws for slaves and masters, rulers and ruled, husbands and wives, parents and children, marriage and celibacy, self-discipline and indulgence, wisdom and ignorance, circumcision and uncircumcision, Christ and the world, the flesh and the spirit. On behalf of some he gives thanks, others he upbraids. Some he names his joy and crown, others he charges with folly. Some who hold a straight course he accompanies, sharing in their zeal; others he checks, who are going wrong. …

[25.] Or perhaps the anathema pronounced on any one who should preach another Gospel than that which had been preached was meant for those times, not for the present. Then, also, the exhortation, “Walk in the Spirit and ye shall not fulfil the lust of the flesh,” was meant for those times, not for the present. But if it be both impious and pernicious to believe this, then it follows necessarily, that as these injunctions are to be observed by all ages, so those warnings also which forbid alteration of the faith are warnings intended for all ages. To preach any doctrine therefore to Catholic Christians other than what they have received never was lawful, never is lawful, never will be lawful: and to anathematize those who preach anything other than what has once been received, always was a duty, always is a duty, always will be a duty.