All strife against sin and its desires is to be preceded by fasting, especially if one is combating inward sin…Fasting is the strengthening of all virtues, the beginning of the struggle, the beauty of virginity and sanctity, the preservation of chastity, the beginning of the way of Christianity, the father of prayer…, for as soon as man begins to fast his mind will be desirous of intercourse with God. Fasting is a storehouse of all virtues, and he that despises it makes all virtues totter. . .As the first commandment imposed upon our nature in the beginning was against the tasting of the food, and in this point the head of our race fell, therefore those who strive for the fear of God begin the building where the first injury originated…Also our Savior began from this point…He fasted forty days and forty nights, and all those who follow His steps base the beginning of their struggle upon this action. That weapon was polished by God, who should despise it without being blameworthy?
-St. Isaac the Syrian When the body is weak by fasting and mortification, the soul is spiritually strong through prayer.
-St. Isaac the Syrian
A full stomach shrinks from examining spiritual questions…A mind full of the world cannot approach the investigation of divine service. Fire cannot burn fresh wood; the love of God cannot be kindled in a heart that loves comfort.
-St. Isaac the Syrian
Just as the most bitter medicine drives out poisonous creatures, so prayer and fasting drives away evil thoughts.
He who prays and fasts is more disposed for almsgiving. He who fasts is light and winged, and prays with wakefulness, and quenches his wicked lusts, and propitiates God, and humbles his soul when lifted up.
-St. John Chrysostom
We seek solitude and submit to fastings, vigils, toils, reading and all other virtue: that through them we may be enabled to prepare our heart and to keep it unharmed by evil passions; and resting on these steps to mount to the perfection of charity which is purity of heart.
-St. John Cassian
For what advantage shall we gain by abstinence from meats, if we do not also expel the evil habits of the soul? Behold, we have spent all of this day fasting; and in the evening we shall spread a table, not such as we did last night, but in a different and more solemn way.
Can any one of us then say that he has changed his life today; that he has changed his bad habit as well as his food? I do not think so! What is the purpose then for our fasting? Why do I exhort and I will not cease to exhort, that undertaking each precept separately, you should spend two or three days in the attainment of it; and just as there are some who rival one another in fasting, and show a marvelous emulation in it; (some indeed who spend two whole days without food; and others who, rejecting from their tables not only the use of wine, and of oil, but of every dish, and taking only bread and water, persevere in this practice during the whole of Lent); so, indeed, let us also contend mutually with one another in abolishing the frequency of oaths. For this is more useful than any fasting; this is more profitable than any strictness.
And this same care which we display in abstaining from food, let us exhibit with respect to abstinence from oaths; since we shall be chargeable with the reproach of extreme folly, while we regard not things that are forbidden, and expend all our care upon things indifferent; for to eat is not forbidden, but to swear is forbidden; we, however, abstaining from those things that are permitted, daringly venture upon those things that are forbidden!
On this account I beseech your Charity to make some change, and to let the beginning of it be visible from today. For if we spend all of this present fast with such zeal, having in this week attained the practice of not swearing at all; and in the following having extinguished wrath; and in that which succeeds it, having pulled up evil-speaking by the roots; and after that, having amended what yet remains; thus going forward in our course, we shall come by little and little to the very summit of virtue; and we shall escape the present danger; and shall make God propitious; and the multitude will come back again to our city; and we shall teach the fugitives that we are to place our hopes of safety neither in security of place, nor in flight and retirement; but in piety of soul, and in virtue of manners. And thus shall we obtain the good things of this and of the future life; which, God grant! we my all be found worthy of, by the grace and loving-kindness of our Lord Jesus Christ, through whom and with whom be glory to the Fr., together with the Holy Spirit, now and for ever and ever. Amen.
-St. John Chrysostom