Isaias 58:5

He says then to them again concerning these things, “Why do ye fast to Me as on this day, saith the Lord, that your voice should be heard with a cry? I have not chosen this fast, saith the Lord, that a man should humble his soul. Nor, though ye bend your neck like a ring, and put upon you sackcloth and ashes, will ye call it an acceptable fast.” To us He saith, “Behold, this is the fast that I have chosen, saith the Lord, not that a man should humble his soul, but that he should loose every band of iniquity, untie the fastenings of harsh agreements, restore to liberty them that are bruised, tear in pieces every unjust engagement, feed the hungry with thy bread, clothe the naked when thou seest him, bring the homeless into thy house, not despise the humble if thou behold him, and not [turn away] from the members of thine own family. …

“Learn, therefore, to keep the true fast of God, as Isaiah says, that you may please God. Isaiah has cried thus: ‘Shout vehemently, and do not spare: lift up thy voice as with a trumpet, and show My people their transgressions, and the house of Jacob their sins. They seek Me from day to day, and desire to know My ways, as a nation that did righteousness, and forsook not the judgment of God. They ask of Me now righteous judgment, and desire to draw near to God, saying, Wherefore have we fasted, and Thou seest not? and afflicted our souls, and Thou hast not known? Because in the days of your fasting you find your own pleasure, and oppress all those who are subject to you. Behold, ye fast for strifes and debates, and smite the humble with your fists. …

“Hear, then,” says he, “foolish man, how grief crushes out the Holy Spirit, and on the other hand saves. When the doubting man attempts any deed, and fails in it on account of his doubt, this grief enters into the man, and grieves the Holy Spirit, and crushes him out. Then, on the other hand, when anger attaches itself to a man in regard to any matter, and he is embittered, then grief enters into the heart of the man who was irritated, and he is grieved at the deed which he did, and repents that he has wrought a wicked deed. This grief, then, appears to be accompanied by salvation, because the man, after having done a wicked deed, repented. Both actions grieve the Spirit: doubt, because it did not accomplish its object; and anger grieves the Spirit, because it did what was wicked. Both these are grievous to the Holy Spirit, doubt and anger. …

For, so far as pertains to fasts, they oppose to us the definite days appointed by God: as when, in Leviticus, the Lord enjoins upon Moses the tenth day of the seventh month (as) a day of atonement, saying, “Holy shall be to you the day, and ye shall vex your souls; and every soul which shall not have been vexed in that day shall be exterminated from his people.” At all events, in the Gospel they think that those days were definitely appointed for fasts in which “the Bridegroom was taken away;” and that these are now the only legitimate days for Christian fasts, the legal and prophetical antiquities having been abolished: for wherever it suits their wishes, they recognise what is the meaning of “the Law and the prophets until John.” Accordingly, (they think) that, with regard to the future, fasting was to be indifferently observed, by the New Discipline, of choice, not of command, accord …

4. Finally, beloved brethren, the divine admonition in the Scriptures, as well old as new, has never failed, has never been silent in urging God’s people always and everywhere to works of mercy; and in the strain and exhortation of the Holy Spirit, every one who is instructed into the hope of the heavenly kingdom is com manded to give alms. God commands and prescribes to Isaiah: “Cry,” says He, “with strength, and spare not. Lift up thy voice as a trumpet, and declare to my people their transgressions, and to the house of Jacob their sins.” And when He had commanded their sins to be charged upon them, and with the full force of His indignation had set forth their iniquities, and had said, that not even though they should use supplications, and prayers, and fastings, should they be able to make atonement for their sins; nor, if they were clothed in sackcloth and ashes, be able to soften G …

In Isaiah: “Cry aloud,” saith He, “and spare not; lift up thy voice like a trumpet; tell my people their sins, and the house of Jacob their wickednesses. They seek me from day to day, and desire to know my ways, as a people which did righteousness, and did not forsake the judgment of God. They ask of me now a righteous judgment, and desire to approach to God, saying, What! because we have fasted, and Thou hast not seen: we have humiliated our souls, and Thou hast not known. For in the days of fasting are found your own wills; for either ye torment those who are subjected to you, or ye fast for strifes and judgments, or ye strike your neighbours with fists. For what do you fast unto me, that to-day your voice should be heard in clamour? This fast I have not chosen, save that a man should humble his soul. …

14. For all these things then let us give thanks to God who loveth man; and for His tender care over us, render Him a recompense, that will also be profitable to ourselves; and as regards the commandment which I so frequently discourse of to you, let us use our utmost diligence! For I will not desist from the exhortation until ye are amended: seeing that what we aim at is not that we may address you seldom or frequently, but that we may continue speaking till we have persuaded you. …

4. For since, as I before said, there are divers proclamations, listen, as in a figure, to the prophet blowing the trumpet; and further, having turned to the truth, be ready for the announcement of the trumpet, for he saith, ‘Blow ye the trumpet in Sion: sanctify a fast.’ This is a warning trumpet, and commands with great earnestness, that when we fast, we should hallow the fast. For not all those who call upon God, hallow God, since there are some who defile Him; yet not Him, that is impossible, but their own mind concerning Him; for He is holy, and has pleasure in the saints. …

37. Farther, although the apostle bids us to “pray without ceasing,” and although to the saints their very sleep is a supplication, we ought to have fixed hours of prayer, that if we are detained by work, the time may remind us of our duty. Prayers, as every one knows, ought to be said at the third, sixth and ninth hours, at dawn and at evening. No meal should be begun without prayer, and before leaving table thanks should be returned to the Creator. We should rise two or three times in the night, and go over the parts of Scripture which we know by heart. When we leave the roof which shelters us, prayer should be our armor; and when we return from the street we should pray before we sit down, and not give the frail body rest until the soul is fed. In every act we do, in every step we take, let our hand trace the Lord’s cross. Speak against nobody, and do not slander your mother’s son. …

59. Joel again summons us to wailing, and will have the ministers of the altar lament under the presence of famine: so far is he from allowing us to revel in the misfortunes of others: and, after sanctifying a fast, calling a solemn assembly, and gathering the old men, the children, and those of tender age, we ourselves must further haunt the temple in sackcloth and ashes, prostrated right humbly on the ground, because the field is wasted, and the meat-offering and the drink-offering is cut off from the house of the Lord, till we draw down mercy by our humiliation.

And so that it is a thing indifferent is very clearly shown from this also; viz., because as it brings justification when observed, so it does not bring condemnation when it is broken in upon; unless perhaps the transgression of a command rather than the partaking of food brings punishment. But in the case of a thing that is good in its own nature, no time should be without it, in such a way as that a man may do without it, for if it ceases, the man who is careless about it is sure to fall into mischief. Nor again is any time given for what is bad in its own nature, because what is hurtful cannot help hurting, if it is indulged in, nor can it ever be made of a praiseworthy character. …

Thus the gluttonous are to be admonished, that in giving themselves to the enjoyment of dainties they pierce not themselves through with the sword of lechery; and that they perceive how great loquacity, how great levity of mind, lie in wait for them through eating; lest, while they softly serve the belly, they become cruelly bound in the nooses of vice. For by so much the further do we go back from our second parent as by immoderate indulgence, when the hand is stretched out for food, we renew the fall of our first parent. But, on the other hand, the abstinent are to be admonished ever anxiously to look out, lest, while they fly the vice of gluttony, still worse vices be engendered as it were of virtue lest, while they macerate the flesh, their spirit break out into impatience; and so there be no virtue in the vanquishing of the flesh, the spirit being overcome by anger. …