1 [The apostle], foreseeing the wicked speeches of unbelievers, has particularized the works which he terms carnal; and he explains himself, lest any room for doubt be left to those who do dishonestly pervert his meaning, thus saying in the Epistle to the Galatians: “Now the works of the flesh are manifest, which are adulteries, fornications, uncleanness, luxuriousness, idolatries, witchcrafts, hatreds, contentions jealousies, wraths, emulations, animosities, irritable speeches, dissensions, heresies, envyings, drunkenness, carousings, and such like; of which I warn you, as also I have warned you, that they who do such things shall not inherit the kingdom of God.” Thus does he point out to his hearers in a more explicit manner what it is [he means when he declares], “Flesh and blood shall not inherit the kingdom of God.” For they who do these things, since they do indeed walk after the flesh, have not the power of living unto God. And then, again, he proceeds to tell us the spiritual actions which vivify a man, that is, the engrafting of the Spirit; thus saying, “But the fruit of the Spirit is love, joy, peace, long-suffering, goodness, benignity, faith, meekness, continence, chastity: against these there is no law.” As, therefore, he who has gone forward to the better things, and has brought forth the fruit of the Spirit, is saved altogether because of the communion of the Spirit; so also he who has continued in the aforesaid works of the flesh, being truly reckoned as carnal, because he did not receive the Spirit of God, shall not have power to inherit the kingdom of heaven. As, again, the same apostle testifies, saying to the Corinthians, “Do you not know that the unrighteous shall not inherit the kingdom of God? Do not err,” he says: “neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind, nor thieves, nor covetous, nor revilers, nor rapacious persons, shall inherit the kingdom of God. And these you indeed have been; but you have been washed, but you have been sanctified, but you have been justified in the name of the Lord Jesus Christ, and in the Spirit of our God.” He shows in the clearest manner through what things it is that man goes to destruction, if he has continued to live after the flesh; and then, on the other hand, [he points out] through what things he is saved. Now he says that the things which save are the name of our Lord Jesus Christ, and the Spirit of our God.
2. Since, therefore, in that passage he recounts those works of the flesh which are without the Spirit, which bring death [upon their doers], he exclaimed at the end of his Epistle, in accordance with what he had already declared, “And as we have borne the image of him who is of the earth, we shall also bear the image of Him who is from heaven. For this I say, brethren, that flesh and blood cannot inherit the kingdom of God.” Now this which he says, “as we have borne the image of him who is of the earth,” is analogous to what has been declared, “And such indeed you were; but you have been washed, but you have been sanctified, but you have been justified in the name of our Lord Jesus Christ, and in the Spirit of our God.” When, therefore, did we bear the image of him who is of the earth? Doubtless it was when those actions spoken of as “works of the flesh” used to be wrought in us. And then, again, when [do we bear] the image of the heavenly? Doubtless when he says, “You have been washed,” believing in the name of the Lord, and receiving His Spirit. Now we have washed away, not the substance of our body, nor the image of our [primary] formation, but the former vain conversation. In these members, therefore, in which we were going to destruction by working the works of corruption, in these very members are we made alive by working the works of the Spirit.
Source: Adversus haereses (New Advent)