St. John Chrysostom – “The Nicene and Post-Nicene Fathers of the Christian Church,” Volume 9.
I speak not, indeed, of such a fast as most persons keep, but of real fasting; not merely an abstinence from meats; but from sins too.
For the nature of a fast is such, that it does not suffice to deliver those who practice it, unless it be done according to a suitable law. “For the wrestler,” it is said, “is not crowned unless he strive lawfully.”
To the end then, that when we have gone through the labor of fasting, we forfeit not the crown of fasting, we should understand how, and after what manner, it is necessary to conduct this business; since that Pharisee also fasted, but afterwards when down empty, and destitute of the fruit of fasting.
The Publican fasted not; and yet he was accepted in preference to him who had fasted; in order that thou mayest learn that fasting is unprofitable, except all other duties follow with it.
The Ninevites fasted, and won the favor of God.
The Jews fasted too, and profited nothing, nay they departed with blame.
Since then the danger in fasting is so great to those who do not know how they ought to fast, we should learn the laws of this exercise, in order that we may not “run uncertainly,” nor “beat the air,” nor while we are fighting contend with a shadow.
Fasting is a medicine; but a medicine, though it be never so profitable, becomes frequently useless owing to the unskillfulness of him who employs it. For it is necessary to know, moreover, the time when it should be applied, and the requisite quantity of it; and the temperament of body that admits it; and the nature of the country, and the season of the year; and the corresponding diet; as well as various other particulars; any of which, if one overlooks, he will mar all the rest that have been named.
Now if, when the body needs healing, such exactness is required on our part, much more ought we, when our care is about the soul, and we seek to heal the distempers of the mind, to look, and to search into every particular with the utmost accuracy.
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, but 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.