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.
Suppose you have ordered yourself not to eat fish; you will find that the enemy continually makes you long to eat it. You are filled with an uncontrollable desire for the thing that is forbidden. In this way you can see how Adam's fall typifies what happens to all of us. Because he was told not to eat from a particular tree, he felt irresistibly attracted to the one thing that was forbidden him.
Concerning fasting, do not grieve, as I have said to you before: God does not demand of anyone labors beyond his strength. And indeed, what is fasting if not a punishment of the body in order to humble a healthy body and make it infirm for passions, according to the word of the Apostle: 'When I am weak, then am I strong' (II Corinthians 12:10).
I shall speak first about control of the stomach, the opposite to gluttony, and about how to fast and what and how much to eat. I shall say nothing on my own account, but only what I have received from the Holy Fathers. They have not given us only a single rule for fasting or a single standard and measure for eating, because not everyone has the same strength; age, illness or delicacy of body create differences. But they have given us all a single goal: to avoid over-eating and the filling of our bellies... A clear rule for self-control handed down by the Fathers is this: stop eating while still hungry and do not continue until you are satisfied.
If a king wanted to take possession of his enemy's city, he would begin by cutting off the water and the food and so his enemies, dying of hunger, would submit to him. It is the same with the passions of the flesh; if a man goes about fasting and hungry the enemies of his soul grow weak.
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.
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.
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.
Fasting is absolutely indispensable for man. From the external aspect, it is a struggle of filial obedience to God, Who has given us the rules of fasting through His Holy Spirit. From the inner aspect, fasting is a struggle of restraint and self-limitation. In this lies the great value and sense of fasting, since a strict observance of fasts tempers one's will and perfects the character of one who is firm in his religious convictions and actions. Let us not forget that Christ Himself fasted, and foretold that His apostles would also fast.
According to St. Gregory the Sinaite there are three degrees in eating: temperance, sufficiency, and satiety. Temperance is when someone wants to eat some more food but abstains, rising from the table still somewhat hungry. Sufficiency is when someone eats what is needed and sufficient for normal nourishment. Satiety is when someone eats more than enough and is more than satisfied. Now if you cannot keep the first two degrees and you proceed to the third, then, at least, do not become a glutton, remembering the words of the lord: 'Woe unto you that are full now, for you shall hunger' (Lk. 6:25). Remember also that rich man who ate in this present life sumptuously every day, but who was deprived of the desired bosom of Abraham in the next life, simply because of this sumptuous eating.
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.
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.
Fasting was ordained in Paradise. The first injunction was delivered to Adam, ‘Of the tree of the knowledge of good and evil you shall not eat.’ ‘You shall not eat’ is a law of fasting and abstinence. The general argument is rather against excess than in support of ceremonial abstinence. In Paradise there was no wine, no butchery of beasts, no eating of flesh. Wine came in after the flood. Noah became drunk because wine was new to him. So fasting is older than drunkenness. Esau was defiled, and made his brother’s slave, for the sake of a single meal. It was fasting and prayer which gave Samuel to Hannah. Fasting brought forth Samson. Fasting begets prophets, strengthens strong men. Fasting makes lawgivers wise, is the soul’s safeguard, the body’s trusty comrade, the armor of the champion, the training of the athlete.
Fasting is an ordinance of the Church, obliging the Christian to observe it on specific days. Concerning fasting, our Savior teaches: 'When thou fastest, anoint thine head, and wash thy face; that thou appear not unto men to fast, but unto thy Father Who is in secret: and thy Father, Who seeth in secret, shall reward thee openly.' From what the Savior teaches we learn (a) that fasting is pleasing to God, and (b) that he who fasts for the uplifting of his mind and heart towards God shall be rewarded by God, Who is a most liberal bestower of Divine gifts, for his devotion. In the New Testament fasting is recommended as a means of preparing the mind and the heart for divine worship, for long prayer, for rising from the earthly, and for spiritualization.
