This is from the first Latin commentary on Paul’s works, specifically at Galatians 2.20–21:
But as I now live in the flesh, I live in the faith of God and Christ. This is truly to live spiritually: that although one lives in the flesh, one does not live on account of the flesh or based on the flesh. Rather, one lives to God and to Christ by faith in them. This is what it means to live spiritually: to meditate on Christ, to speak of him, to believe him, to direct one’s desires toward him; to flee the world, to expel from one’s mind all things which are in the world. This is what it means to live by faith: to hope for no other good than what is from Christ and from God. This is what it means to live in the faith of God and Christ, who loved me and handed himself over for my sake. Let us keep this worthy act in mind, so that we live in him through faith—in him, who to hand over so great a gift to us would give himself to death and the cross for our sake, and in so doing liberate us from our sins.
Next he adds in this manner:
I am not ungrateful to God’s grace (2: 21), so that, God having redeemed me through Christ and Christ having handed himself over for my sake, I would return to the hope of the Law—all the hope I have in Christ being disregarded—and would believe myself to be justified based on the works of the Law. That would be ungrateful to the one who did so much for me, who for my sake would put himself in the line of fire in order to liberate me from my sins by taking their penalties upon himself.
That last line is a killer.