The man who during his whole life loves the conversation of this yoke-mate fasting is a friend of chastity. Just as the satisfaction of the belly is the source of all evils, and as the slackness of sleep kindles the lust of fornication, so fasting, vigil, and wakefulness in God’s service by withstanding the sweetness of sleep through crucifying the body throughout the day and night, are God’s holy pathway and the foundation of every virtue. Fasting is the champion of every virtue, the beginning of the struggle, the crown of the abstinent, the beauty of virginity and sanctity, the resplendence of chastity, the commencement of the path of Christianity, the mother of prayer, the well-spring of sobriety and prudence, the teacher of stillness, and the precursor of all good works. Just as the enjoyment of light is coupled with healthy eyes, so desire for prayer accompanies fasting that is practiced with discernment.
When a man begins to fast, he straightway yearns in his mind to enter into converse with God. For the body that fasts cannot endure to sleep upon its pallet all the night through. Fasting naturally incites wakefulness unto God, not only during the day, but also at night. For the empty body of a faster is not greatly wearied by the battle against sleep. And even if his senses are weakened, his mind is wakeful unto God in prayer. It is better for a man to desist from his liturgy because of weakness due to fasting, than because of sloth due to eating. When the seal of fasting is set upon a man’s lips, his thought reflects with compunction, his heart pours forth prayer, gloom lies upon his countenance, shameful thoughts are far removed from him, cheer cannot be detected in his eyes, and he is an enemy of lusts and vain conversations. No one has ever seen a discerning faster enslaved by evil desires. Fasting with discernment is a spacious mansion for every good thing; but he who neglects fasting makes every good totter. For fasting was the commandment that was given to our nature in the beginning to protect it with respect to the tasting of food, and in this point the progenitor of our substance fell. There, however, where the first defeat was suffered, the ascetic strugglers make their beginning in the fear of God as they start to keep His laws.
And the Saviour also, when He manifested Himself to the world in the Jordan, began at this point. For after His baptism the Spirit led Him into the wilderness and He fasted for forty days and forty nights. Likewise all who set out to follow in His footsteps make the beginning of their struggle upon this foundation. For this is a weapon forged by God, and who shall escape blame if he neglects it? And if the Lawgiver Himself fasts, who among those who keep the law has no need of fasting? This is why the human race knew no victory before fasting, and the devil had never experienced defeat from our nature; but this weapon has made him powerless from the outset. Our Lord was the firstborn Leader of victory, so as to set the first crown of victory upon the head of our nature. When the devil, that foe and tyrant, sees a man bearing this weapon, he is straightway frightened and he recollects and considers that defeat which he suffered in the wilderness at the hands of the Saviour; at once his strength is shattered and the very sight of this weapon, given us by our Commander-in-chief, burns him. What weapon is more powerful and gives more boldness to the heart in the time of battle against the spirits of wickedness, than hunger endured for Christ’s sake? For the more the body toils and endures hardship when the phalanx of the demons encompasses a man, the more his heart is given succour by the power of confidence. He who has armed himself with the weapon of fasting is afire with zeal at all times. Elias the zealot also pursued the work of fasting when he was zealous for God’s law. Furthermore, fasting reminds the faster of the commandments of the Spirit and it is an intermediary between the old Law and the grace given us by Christ. He who is negligent with respect to fasting is slothful, heedless, and feeble in the other ascetical struggles as well and he manifests an inception and an evil token of slackness in his soul, thus giving his antagonist an opportunity for defeating him. It is evident that he who enters naked and unarmed into the struggle will retreat from it without gaining the victory; for his limbs were not shielded with the warmth of fasting’s hunger. Such is the nature of fasting, that whoever perseveres in it will possess an unshakeable mind, one ready to encounter and repel all the troublesome passions.
It is said concerning many of the martyrs, that when they foreknew, either by revelation or by information received from one of their friends, the day on which they were to receive the crown of martyrdom, they did not taste anything the preceding night, but from evening till morning they stood keeping vigil in prayer, glorifying God in psalms, hymns, and spiritual odes, and they looked forward to that hour with joy and exultation, waiting to meet the sword in their fast as ones prepared for the nuptials. Therefore let us also be vigilant, we who are called to an unseen martyrdom so as to receive the crowns of sanctification, so that we may never give our enemies a sign of denial with any member or part of our body.
St Isaac the Syrian, First Collection, from Homily 37.