Romans 15:13

"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.