16 knowing that a man is not justified by the works of the law but by faith in Jesus Christ, even we have believed in Christ Jesus, that we might be justified by faith in Christ and not by the works of the law; for by the works of the law no flesh shall be justified. 17 But if, while we seek to be justified by Christ, we ourselves also are found sinners, is Christ therefore a minister of sin? Certainly not! 18 For if I build again those things which I destroyed, I make myself a transgressor. 19 For I through the law died to the law that I might live to God. 20 I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me.
Marius Victorinus said in his Epistle to the Galatians:
“Suppose that we, after receiving faith in Christ, do in Christ what the Jews do. Suppose we have received faith in Christ and wish to be justified in it. Suppose we have understood that a man is not justified by the works of the law. Would we not then, by observing the works of the law, be made sinners? Then it would be the case that Christ, whom we received in order not to sin, would himself become a minister of sin. Now, when after receiving him we return to sin – that is, to the old covenant – is Christ made a minister of sin? Let this possibility, Paul says, be far from us. One ought not to think in this way and act so as to make Christ a minister of sin, when he suffered in order than sin might perish.”
St. John Chrysostom in his Homily on Galatians said:
“Note the shrewdness of Paul. For they wanted to show that the one who does not keep the law is a transgressor; but he turns the argument upside down, showing that the one who observes the law is a transgressor not against faith but against the law itself. What he says is as follows: ‘The law has ceased, as we ourselves agree, in so far as we have left it and taken refuge in the salvation of faith. If we not strive to establish it, we become transgressors by this very fact, as we strive to observe the precepts dissolved by God.”
St. Augustine wrote in On Continence:
“The human spirit, cleaving to the Spirit of God, struggles against the flesh that is, against itself and on its own behalf. Those impulses natural to humanity, whether in the flesh or in the soul, which remain because of our acquired debility, are restrained by discipline for the sake of obtaining salvation. So the human being who does not live according to human nature can already say, ‘I live, yet not I, but Christ lives in me.’ For where I am not I, I am more happily I. Thus when any reprobate impulse arises according to my old human nature, to which I who serve the law of God with my mind do not consent, I may now say this: ‘now I am not the one doing that.'”