Nicene and Post-Nicene Fathers: Series II/Volume XI/John Cassian/The Twelve Books/Book V/Chapter 21

Chapter XXI.

Of the inward peace of a monk, and of spiritual abstinence.

it is not an external enemy whom we have to dread. Our foe is shut up within ourselves: an internal warfare is daily waged by us: and if we are victorious in this, all external things will be made weak, and everything will be made peaceful and subdued for the soldier of Christ. We shall have no external enemy to fear, if what is within is overcome and subdued to the spirit. And let us not believe that that external fast from visible food alone can possibly be sufficient for perfection of heart and purity of body unless with it there has also been united a fast of the soul. For the soul also has its foods which are harmful, fattened on which, even without superfluity of meats, it is involved in a downfall of wantonness. Slander is its food, and indeed one that is very dear to it. A burst of anger also is its food, even if it be a very slight one; yet supplying it with miserable food for an hour, and destroying it as well with its deadly savour. Envy is a food of the mind, corrupting it with its poisonous juices and never ceasing to make it wretched and miserable at the prosperity and success of another. Kenodoxia, i.e., vainglory is its food, which gratifies it with a delicious meal for a time; but afterwards strips it clear and bare of all virtue, and dismisses it barren and void of all spiritual fruit, so that it makes it not only lose the rewards of huge labours, but also makes it incur heavier punishments. All lust and shifty wanderings of heart are a sort of food for the soul, nourishing it on harmful meats, but leaving it afterwards without share of the heavenly bread and of really solid food. If then, with all the powers we have, we abstain from these in a most holy fast, our observance of the bodily fast will be both useful and profitable. For labour of the flesh, when joined with contrition of the spirit, will produce a sacrifice that is most acceptable to God, and a worthy shrine of holiness in the pure and undefiled inmost chambers of the heart. But if, while fasting as far as the body is concerned, we are entangled in the most dangerous vices of the soul, our humiliation of the flesh will do us no good whatever, while the most precious part of us is defiled: since we go wrong through that substance by virtue of which we are made a shrine of the Holy Ghost. For it is not so much the corruptible flesh as the clean heart, which is made a shrine for God, and a temple of the Holy Ghost. We ought therefore, whenever the outward man fasts, to restrain the inner man as well from food which is bad for him: that inner man, namely, which the blessed Apostle above all urges us to present pure before God, that it may be found worthy to receive Christ as a guest within, saying &#8220;that in the inner man Christ may dwell in your hearts through faith.&#8221;