Romans 16:20

The grace of our Lord Jesus Christ be with you. The grace of God and the grace of our Lord Jesus Christ are to be taken as one and the same grace. For just as the Father gives life to whom he wills, so also the Son gives life to whom he wills; and just as the Father has life in himself, and has granted to the Son to have life in himself, so also the grace which the Father gives, this the Son likewise gives. Yet it must be understood that everything which human beings have from God is grace, for they have nothing by right of debt. For who has first given to him, and it shall be repaid to him? Grace, then, is whatever he possesses who once was not and now is, receiving it from him who always was, and is, and shall be forever.

And after that let him proclaim: Ye penitents, pray; let us all earnestly pray for our brethren in the state of penitence, that God, the lover of compassion, will show them the way of repentance, and accept their return and their confession, and bruise Satan under their feet suddenly, and redeem them from the snare of the devil, and the ill-usage of the demons, and free them from every unlawful word, and every absurd practice and wicked thought; forgive them all their offences, both voluntary and involuntary, and blot out that handwriting which is against them, and write them in the book of life; cleanse them from all filthiness of flesh and spirit, and restore and unite them to His holy flock.

After revealing the enemy, Paul points to the Savior. Those who receive God's grace will never be defeated.

For, in the proceedings before the proconsul; as a good and true teacher you first have pronounced that which we your disciples, following you, ought to say before the president. And, as a sounding trumpet, you have stirred up God's soldiers, furnished with heavenly arms, to the close encounter; and fighting in the first rank, you have slain the devil with a spiritual sword: you have also ordered the troops of the brethren, on the one hand and on the other, with your words, so that snares were on all sides laid for the enemy, and the severed sinews of the very carcase of the public foe were trodden under foot. Believe us, dearest, that your innocent spirit is not far from the hundred-fold reward, seeing that it has feared neither the first onsets of the world, nor shrunk from going into exile, nor hesitated to leave the city, nor dreaded to dwell in a desert place; and since it furnished many with an example of confession, itself first spoke the martyr-witness. For it provoked others to acts of martyrdom by its own example; and not only began to be a companion of the martyrs already departing from the world, but also linked a heavenly friendship with those who should be so.

"And the God of peace shall bruise Satan under your feet shortly." For since he had spoken of those who "caused divisions and offences among them," he has mentioned "the God of peace" also, that they might feel hopeful about the riddance of these evils. For he that rejoiceth in this (i. e., peace) will put an end to that which makes havoc of it. And he does not say, will subject, but "will bruise," which is a stronger expression. And not those people only, but also him who was the general over them herein, Satan. And not "will bruise" merely, but "under your feet," so that they may obtain the victory themselves, and become noble by the trophy. And the time again is made a ground of comfort. For he adds, "shortly." And this was prayer and prophecy as well at once. "The grace of our Lord Jesus Christ be with you." That greatest weapon; that impregnable wall; that tower unshaken! For he reminds them of the grace, that he may give them the more alacrity. Because if ye have been freed from the ills more grievous by far, and freed by grace only, much more will ye be freed from the lesser, now ye have become friends too, and contribute your own share likewise. You see how he neither puts prayer without works, nor works without prayer. For after giving them credit for their obedience, then he prays; to show that we need both, our own part as well as God's part, if we are to be duly saved. For it was not before only, but now too, even though we be great and in high esteem, we need grace from Him.