Selected Quotes of the Fathers on Fasting
"...We must then so moderate our rightful use of food that our other desires may be subject to the same rule. For this is also a time of peace and serenity, in which having put away all stains of evil doing we strive after steadfastness in what is good. Now is the time when generous Christian souls forgive offences, pay no heed to insults, and wipe out the memory of past injuries. Now let the Christian soul exercise itself in the armour of justice, on the right hand and on the left, so that amid honour and dishonour, evil report and good, the praise of men will not make proud the virtue that is well rooted, the conscience that has peace, nor dishonour cast it down. The moderation of those who worship God is not melancholy, but blameless."
St. Leo the Great - "Lent the Season of Purification" (The Sunday Sermons of the Great Fathers)
"If anyone, while keeping fast, adds something to it by his own will, or if he fasts seeking men's praise or some gain from it, such a fast is abomination in the eyes of God. And so it is in all things. Every good action, which is done not merely from the love of God, but is mingled with one's own will, is unclean and unpleasing to God."
St. Barsanuphius and St. John - 'Directions in Spiritual Work' (The Philokalia)"
"And though every day a man lives may rightly be a day of repentance, yet is it in these days more becoming, more appropriate, to confess our sins, to fast, and to give alms to the poor; since in these days you may wash clean the sins of the whole year."
St. John Chrysostom - "The Sunday Sermons of the Great Fathers"
"It is remarkable that, however much we trouble about our health, however much care we take of ourselves, whatever wholesome and pleasant food and drink we take, however much we walk in the fresh air, still, notwithstanding all this, in the end we sicken and corrupt; whilst the saints, who despise the flesh, and mortify it by continual abstinance and fasting, by lying on the bare earth, by watchfulness, labours, unceasing prayer, make both their souls and bodies immortal. Our well-fed bodies decay and after death emit an offensive odour, whilst theirs remain fragrant and flourishing both in life and after death. It is a remarkable thing: we, by building up our body, destroy it, whilst they, by destroying theirs, build it up - by caring only for the fragrance of their souls before God, they obtain fragrance of the body also."
St. John of Kronstadt - 'My Life in Christ'"
"The heart cannot remain firm in purity, so as not to be defiled, if it will not be crushed by fasting. It is impossible also to preserve holiness without fasting, and the flesh will not submit to the spirit for spiritual activity, and prayer itself will not rise up and act because natural needs predominate. And the flesh will be compelled to become feverish. And from thoughts the heart is aroused and is defiled, and through this, grace departs, and the unclean spirits have boldness to rule over us as much as they wish."
St. Paisius Velichkovsky - 'Field Flowers'"
"My brethren, it is not possible for these things to come about in one day or one week! They will take much time, labor, and pain, in accordance with each man's attitude and willingness, according to the measure of faith (Rom, 12:3, 6) and one's contempt for the objects of sight and thought. In addition, it is also in accordance with the fervor of his ceaseless penitence and its constant working in the secret chamber of his heart (Mt. 6:6) that this is accomplished more quickly or more slowly by the gift and grace of God. But without fasting no one was ever able to achieve any of these virtues or any others, for fasting is the beginning and foundation of every spiritual activity. Whatever you will build on this foundation cannot collapse or be destroyed, because they are built on solid rock. But if you remove this foundation and substitute for it a full stomach and improper desires, they will be undermined like sand by evil thoughts, and the whole structure of virtues will be destroyed (cf. Mt. 7:26; Lk. 6:49). To prevent this from happening in our case, my brethren, let us gladly stand on the solid foundation of fasting. Let us stand firmly, let us stand willingly!"
St. Symeon the New Theologian - "The Discourses"
"When He had therefore fasted for forty days and for forty nights, and afterwards was hungry, He gave an opportunity to the devil to draw near, so that He might teach us through this encounter how we are to overcome and defeat him. This a wrestler also does. For in order to teach his pupils how to win he himself engages in contests with others, demonstrating on the actual bodies of others that they may learn how to gain the mastery. This is what took place here. For, desiring to draw the devil into contest, He made His hunger known to him. He met him as he approached, and meeting him, with the skill which He alone possessed, He once, twice, and a third time, threw His enemy to the ground."
St. John Chrysostom
"The outward man perishes through fasting and self-control, but the more he does so, the more the inward man is renewed..."
St. Gregory Palamas - "Homilies"
"Do you fast? Give me proof of it by your works. If you see a poor man, take pity on him. If you see a friend being honored, do not envy him. Do not let only your mouth fast, but also the eye, and the ear, and the feet, and the hands, and all the members of our bodies. Let the hands fast, by being free of avarice. Let the feet fast, by ceasing to run after sin. Let the eyes fast, by disciplining them not to glare at that which is sinful... Let the ear fast... by not listening to evil talk and gossip... Let the mouth fast from the foul words and unjust criticism. For what good is it if we abstain from birds and fishes, but bite and devour our brothers?"
St. John Chrysostom - "The Proof of Fasting"
(All quotes taken from: http://scienceofsalvation.blogspot.com)