8. I speak not, indeed, of such a fast as most persons keep, but of real fasting; not merely an abstinence from foods; but from sins too. ... "For the wrestler," it is said, "is not crowned unless he strive lawfully." To the end then, that when we have gone through the labour of fasting, we forfeit not the crown of fasting, .... since that Pharisee also fasted, but afterwards went down empty, and destitute of the fruit of fasting.
St. John Crysostom on Fasting
10. But, as I said before, we may see what it was that dissolved such inexorable wrath. Was it, forsooth, fasting only and sackcloth? We say not so; but the change of their whole life. ... "And God saw their works."..."That they turned every one from their evil ways, and the Lord repented of the evil that He had said He would do unto them." You see, fasting did not rescue from this danger, but it was the change of life, which rendered God merciful and kind to these barbarians? ... for the honour of fasting consists not in abstinence from food, but in withdrawing from sinful practices; ... Are you fasting? Give me proof of it by your works! If you see a poor man, take pity on him! If you see in enemy, be reconciled to him! If you see a friend gaining honour, envy him not If you see a handsome woman, pass her by!
11. For let not the mouth only 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 pure from greed and covetousness. 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, ... 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. Do you 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 gossip.
12. Let the mouth too fast from disgraceful speeches and backbiting. For what doth it profit if we abstain from birds and fishes; and yet bite and devour our brethren? The evil speaker eateth the flesh of his brother, and biteth the body of his neighbour.
St. John Chrysostom: Homilies on the statues homily III ,8-12 (N/PNF Vol I. IX)