The body is a slave, the soul a sovereign, and therefore it is due to Divine mercy when the body is worn out by illness: for thereby the passions are weakened, and a man comes to himself; indeed, bodily illness itself is sometimes caused by the passions.
Sear your loins by abstaining from food, and prove your heart by controlling your speech, and you will succeed in bringing the desiring and incensive powers of your soul into the service of what is noble and good.
If you have promised Christ to go by the strait and narrow way, restrain your stomach, because by pleasing it and enlarging it, you break your contract. Attend and you will hear Him who says: 'Spacious and broad is the way of the belly that leads to the perdition of fornication, and many there are who go in by it; because narrow is the gate and strait is the way of fasting that leads to the life of purity, and few there be that find it.'
Fasting is beneficial when it is undertaken for quelling desire, humbling the soul, transforming hatred, extinguishing anger, erasing remembrance of wrongs, and for the purity of the understanding and the practice of prayer.
Once two brethren came to a certain elder whose custom it was not to eat every day. But when he saw the brethren he invited them with joy to dine with him, saying: Fasting has its reward, but he who eats out of charity fulfills two commandments, for he sets aside his own will and he refreshes his hungry brethren.
To what end do fasting and penitence lead? For what purpose is this trouble taken? They lead to the cleansing of the soul from sins, to peace of heart, to union with God; they fill us with devotion and sonship, and give us boldness before God.
The right practice of abstinence is needful not only to the mortification of the flesh but also to the purification of the mind. For the mind then only keeps holy and spiritual fast when it rejects the food of error and the poison of falsehood.
Fasting needn't be limited to abstinence from food alone, because true fasting is departure from evil deeds. Forgive your neighbor any insult, abstain from causing your neighbor offence, abstain from irritation, from senseless sorrows, from fear, wrath, and so on. ‘True fasting is alienation from evil, temperance of the tongue, setting aside of wrath, casting out of lust, idle talk, lies, and oath-breaking’…This is a true and pleasing fast for the Lord. Departing from these vices and from a corrupt state is what comprises a true fast.
Once two brothers came to a certain old man. It was his custom not to eat every day but when he saw them he received them joyfully and said, 'A fast has its own reward, but he who eats for the sake of love fulfils two commandments: he leaves his own will and he refreshes his brothers.'
Bodily purity is primarily attained through fasting, and through bodily purity comes spiritual purity. Abstinence from food, according to the words of that son of grace, St. Ephraim the Syrian, means: 'Not to desire or demand much food, either sweet or costly; to eat nothing outside the stated times; not to give oneself over to gratification of the appetite; not to stir up hunger in oneself by looking at good food; and not to desire one or another sort of food.
The reason that fasting has an effect on the spirits of evil rests in its powerful effect on our own spirit. A body subdued by fasting brings the human spirit freedom, strength, sobriety, purity, and keen discernment.
We must not only keep a sharp watch over our diet, but keep away from all other kinds of sin so that as our stomach keeps fast, so also may our tongue as we abstain from calumny, from deceit, from idle talk, from railing and anger and all other vices which arise from the tongue. So also let our eyes keep fast. No looking for trivialities, no letting the eyes wander freely, no impudent lying in wait for people to talk to. The same with the hands and feet, to prevent them from doing anything evil. Fasting in this way, as St. Basil says, is an acceptable fast and, leaving behind all the evil to which our senses are inclined, we may come to the holy day of Resurrection, renewed and clean and worthy to share in the Holy Mysteries.
If a person swallows too much food, he is inviting impure thoughts. If he mortifies the stomach, he is creating pure thoughts. Often a lion if it is caressed becomes domesticated, whereas the more you coddle the body, the more it goes wild.
One should not ponder divine matters on a full stomach, say the ascetics. For the well-fed, even the most superficial secrets of the Trinity lie hidden.
Fasting, while of value in itself, is not something to boast of in front of God, for it is simply a tool for training those who desire self-restraint. The ascetic should not feel proud because he fasts; no artist ever boasts that his accomplishment is simply due to his tools; but he waits for the work itself to give proof of his skill.
Fasting is an exceptional virtue; it represses bodily impulses and gives strength to the soul to fight against the poisoning of the heart through the senses, and provides it with a remedy against any past poisoning. Fasting causes the mind to be cleansed constantly. It withers up every evil thought and brings healthy, godly thoughts -- -holy thoughts that enlighten the mind and kindle it with more zeal and spiritual fervor.
Many abstain from meat, milk and other food which God has not forbidden and which was even given as a blessing of people who have learned the truth and know how to partake of these things with thanksgiving (I Tim. 4:34). But the same abstemious, devout-living people, give scandal by their action, and spread scandal with their tongue like an incendiary fire.
And finally, did not the Lord Jesus Himself begin His divine ministry of the salvation of mankind with a long, forty day fast? And did not He, in this way, clearly show that we must make a serious beginning to our life as Christians with fasting? First, the fast, and then all the rest comes together with, and through, the fast. By His own example, the Lord showed us how great a weapon fasting is. With this weapon, He vanquished Satan in the wilderness, and with it was victorious over the three chief satanic passions with which Satan tempted Him: love of ease love of praise and love of money. These are three destructive greeds, the three greatest traps into which the evil enemy of the human race lures Christ's soldiers.