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.
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.
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.
It is necessary most of all for one who is fasting to curb anger, to accustom himself to meekness and condescension, to have a contrite heart, to repulse impure thoughts and desires, to examine his conscience, to put his mind to the test and to verify what good has been done by us in this or any other week, and which deficiency we have corrected in ourselves in the present week. This is true fasting.
If you refuse to accept suffering and dishonor, do not claim to be in a state of repentance because of your other virtues. For self-esteem and insensitivity can serve sin even under the cover of virtue.
I have said these things, not that we may disparage fasting, but that we may honor fasting; for the honor of fasting consists not in abstinence from food, but in withdrawing from sinful practices; since he who limits his fasting only to an abstinence from meats, is one who especially disparages it. Dost thou fast? Give me proof of it by thy works! Is it said by what kind of works? If thou seest a poor man, take pity on him! If thou seest an enemy, be reconciled to him! If thou seest a friend gaining honor, envy him not! If thou seest a handsome woman, pass her by! For let not the mouth only fast, but also the eye, and ear, and the feet, and the hands, and all the members of our bodies. Let the hands fast, by being pure from rapine and avarice. Let the feet fast, by ceasing from running to the unlawful spectacles. Let the eyes fast, being taught never to fix themselves rudely upon handsome countenances, or to busy themselves with strange beauties. For looking is the food of the eyes, but if this be such as is unlawful or forbidden, it mars the fast; and upsets the whole safety of the soul; but if it be lawful and safe, it adorns fasting. For it would be among things the most absurd to abstain from lawful food because of the fast, but with the eyes to touch even what is forbidden. Dost thou not eat flesh? Feed not upon lasciviousness by means of the eyes. Let the ear fast also. The fasting of the ear consists in refusing to receive evil speakings and calumnies. 'Thou shalt not receive a false report,' it says.
In no art do the artists judge the result of their work by the tools they use, but they await the work's completion and by it judge the art. Adopting such a practice with regard to food, not placing all your hope on fasting, but fasting moderately and according to the amount of your strength, strive toward mental activity. In this way you can avoid pride and will not spurn God's good works, sending up praises to God for everything.
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.
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.'
Even a pious person is not immune to spiritual sickness if he does not have a wise guide -- either a living person or a spiritual writer. This sickness is called prelest, or spiritual delusion, imagining oneself to be near to God and to the realm of the divine and supernatural. Even zealous ascetics in monasteries are sometimes subject to this delusion, but of course, laymen who are zealous in external struggles (podvigi) undergo it much more frequently. Surpassing their acquaintances in struggles of prayer and fasting, they imagine that they are seers of divine visions, or at least of dreams inspired by grace. In every event of their lives, they see special intentional directions from God or their guardian angel. And then they start imagining that they are God's elect, and often try to foretell the future. The Holy Fathers armed themselves against nothing so fiercely as against this sickness -- prelest.
Hold faith and humility fast within you; for through them you will find mercy, help, and words spoken by God in the heart, along with a protector who stands beside you both secretly and manifestly.
When you fast and are nourished with abstinence, do not store the leftovers for tomorrow, but, as the Lord became poor and enriched us, feed someone who does not want to be hungry, you who hungers willingly. Then your fast will be like the dove who brings and joyfully proclaims salvation to your soul from the flood.
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.
Fasting was of no benefit to that Pharisee in the Gospel, even though he always fasted two days a week, because he had adulterated it with pride and condemnation of his neighbor (Luke 18:11-12). Not that this means fasting is unprofitable. Moses, Elijah & the Lord Himself showed how beneficial it is for those who fast properly in a way pleasing to God.
People have to answer greatly for not keeping the rules of the Church with respect to the fasts. People justify themselves by saying that they never considered it a sin to eat dairy products during the fasts. They repent and consider themselves sinners in every other respect, but they do not think to repent about not keeping the fasts. Meanwhile, they are transgressing the commandment of our holy Mother, the Church, and according to the teaching of the Apostle Paul, they are as the heathen and publicans because of their disobedience.