Rom 15:13

“Precisely how all this can be fulfilled so that they may be filled with all joy and peace is hard to say, especially since the apostle himself, when talking about the gifts of the Spirit, says that he knows in part and prophesies in part. But I think that believers can have the fullness of peace when they are reconciled to God the Father by faith.… For if someone who believes is armed with the power of the Holy Spirit, it is certain that he will always have the fullness of joy and peace.”

“"Now the God of hope fill you with all joy and peace in believing, that ye may abound in hope, through the power of the Holy Ghost." That is, that ye may get clear of that heartlessness towards one another, and may never be cast down by temptations. And this will be by your abounding in hope. Now this is the cause of all good things, and it comes from the Holy Spirit. But it is not simply from the Spirit, but on condition of our contributing our part also. This is why he says, "in believing." For this is the way for you to be filled with joy, if ye believe, if ye hope. Yet he does not say if ye hope, but, "if ye abound in hope," so as not to find comfort in troubles only, but even to have joy through the abundance of faith and hope. And in this way, ye will also draw the Spirit to you. In this way, when He is come ye will continually keep to all good things. For just as food maintaineth our life, and by this ruleth the body, so if we have good works, we shall have the Spirit; and if we have the Spirit, we shall also have good works. As also, on the other hand, if we have no works, the Spirit flieth away. But if we be deserted by the Spirit, we shall also halt in our works. For when this hath gone, the unclean one cometh: this is plain from Saul. For what if he doth not choke us as he did him, still he strangles us in some other way by wicked works. We have need then of the harp of David, that we may charm our souls with the divine songs, both these, and those from good actions. Since if we do the one only, and while we listen to the charm, war with the charmer by our actions, as he did of old; the remedy will even turn to judgment to us, and the madness become the more furious. For before we heard, the wicked demon was afraid lest we should hear it and recover. But when after hearing it even, we continue the same as we were, this is the very thing to rid him of his fear. Let us sing then the Psalm of good deeds, that we may cast out the sin that is worse than the demon. For a demon certainly will not deprive us of heaven, but doth in some cases even work with the sober-minded. But sin will assuredly cast us out. For this is a demon we willingly receive, a self-chosen madness. Wherefore also it hath none to pity it or to pardon it. Let us then sing charms over a soul in this plight, as well from the other Scriptures, as also from the blessed David. And let the mouth sing, and the mind be instructed. Even this is no small thing. For if we once teach the tongue to sing, the soul will be ashamed to be devising the opposite of what this singeth. Nor is this the only good thing that we shall gain, for we shall also come to know many things which are our interest.”

“He prays that the believers from among the Jews be filled with joy, for they were grieved by reproach, and that the believers from among the Gentiles be filled with peace, for they were hostile toward those who adhered to the law; or rather, he prays that both groups be filled with joy and peace. How then is this to be accomplished? By faith. And what good does faith provide us? Richness in hope. For whoever believes in the future blessings and remains content with the present ones is rich in hope, that is, he awaits the future blessings and endures all temporal afflictions. And what good does hope provide us? The acquisition of the power of the Holy Spirit, which makes our hope most firm. For hope, on the one hand, provides us with the power of the Holy Spirit, and on the other hand, becomes stronger in us through the Holy Spirit.”

“Then when he says, now may the God of hope, he adds a prayer, saying: it has been stated that the gentiles will hope in Christ, the God of hope, i.e., who pours this hope in us: my hope, O Lord (Ps 71:5). Or may the God of hope, i.e., the one to hope in, fill you with all joy, i.e., spiritual, which is concerned with God: the joy of the Lord is your strength (Neh 8:10), and peace, through which a man is at peace in himself and with God and his neighbor: great peace have they who love your law (Ps 119:165), in believing. As if to say: so that along with believing you may have peace and joy, which are effects of charity, as it says in Galatians: the fruit of the Spirit is love, joy, peace (Gal 5:22). Hence it is clear that he wishes them to have from God, the giver of hope, not only faith but charity, through which faith works, as it says in Galatians (Gal 5:6), lest their faith be unformed and dead: faith without works is dead (Jas 2:26). So that by the fullness of these virtues you may abound, by progressing from good to better, not only in hope but also in the power of the Holy Spirit, i.e., in charity, which is poured forth in your hearts by the Holy Spirit, as was said above (Rom 5:5); God is able to provide you with every grace in abundance (2 Cor 7:8).”