5 But if you keep the way of innocence, the way of righteousness, if you walk with a firm and steady step, if, depending on God with your whole strength and with your whole heart, you only be what you have begun to be, liberty and power to do is given you in proportion to the increase of your spiritual grace. For there is not, as is the case with earthly benefits, any measure or stint in the dispensing of the heavenly gift. The Spirit freely flowing forth is restrained by no limits, is checked by no closed barriers within certain bounded spaces; it flows perpetually, it is exuberant in its affluence.
Let our heart only be thirsty, and be ready to receive: in the degree in which we bring to it a capacious faith, in that measure we draw from it an overflowing grace. Thence is given power, with modest chastity, with a sound mind, with a simple voice, with unblemished virtue, that is able to quench the virus of poisons for the healing of the sick, to purge out the stains of foolish souls by restored health, to bid peace to those hat are at enmity, repose to the violent, gentleness to the unruly—by startling threats to force to avow themselves the impure and vagrant spirits that have betaken themselves into the bodies of men whom they purpose to destroy, to drive them with heavy blows to come out of them, to stretch them out struggling, howling, groaning with increase of constantly renewing pain, to beat them with scourges, to roast them with fire: the matter is carded on there, but is not seen; the strokes inflicted are hidden, but the penalty is manifest.
Thus, in respect of what we have already begun to be, the Spirit that we have received possesses its own liberty of action; while in that we have not yet changed our body and members, the carnal view is still darkened by the clouds of this world. How great is this empire of the mind, and what a power it has, not alone that itself is withdrawn from the mischievous associations of the world, as one who is purged and pure can suffer no stain of a hostile irruption, but that it becomes still greater and stronger in its might, so that it can rule over all the imperious host of the attacking adversary with its sway!
Source: The Epistles of Cyprian (New Advent)