3 I have not at my disposal sufficient leisure to enter on the refutation of his opinions one by one: my time is demanded by other and more important work. But if you devote a little more carefully to this treatise of an anonymous Roman author, the talents which by your letters you prove yourself to possess, and which I greatly love in you as God's gift, you will see that he has not hesitated to wound by his most injurious language almost the whole Church of Christ, from the rising of the sun to its going down. Nay, I may say not almost, but absolutely, the whole Church. For he is found to have not even spared the Roman Christians, whose custom he seems to himself to defend; but he is not aware how the force of his invectives recoils upon them, for it has escaped his observation. For when arguments to prove the obligation to fast on the seventh day of the week fail him, he enters on a vehement blustering protest against the excesses of banquets and drunken revelries, and the worst licence of intoxication, as if there were no medium between fasting and rioting. Now if this be admitted, what good can fasting on Saturday do to the Romans? Since on the other days on which they do not fast they must be presumed, according to his reasoning, to be gluttonous, and given to excess in wine. If, therefore, there is any difference between loading the heart with surfeiting and drunkenness, which is always sinful, and relaxing the strictness of fasting, with due regard to self-restraint and temperance on the other, which is done on the Lord's day without censure from any Christian—if, I say, there is a difference between these two things, let him first mark the distinction between the repasts of saints and the excessive eating and drinking of those whose god is their belly, lest he charge the Romans themselves with belonging to the latter class on the days on which they do not fast; and then let him inquire, not whether it is lawful to indulge in drunkenness on the seventh day of the week, which is not lawful on the Lord's day, but whether it is incumbent on us to fast on the seventh day of the week, which we are not wont to do on the Lord's day.
4. This question I would wish to see him investigate, and resolve in such a manner as would not involve him in the guilt of openly speaking against the whole Church diffused throughout the world, with the exception of the Roman Christians, and hitherto a few of the Western communities. Is it, I ask, to be endured among the entire Eastern Christian communities, and many of those in the West, that this man should say of so many and so eminent servants of Christ, who on the seventh day of the week refresh themselves soberly and moderately with food, that they “are in the flesh, and cannot please God;” and that of them it is written, “Let the wicked depart from me, I will not know their way;” and that they make their belly their god, that they prefer Jewish rites to those of the Church, and are sons of the bondwoman; that they are governed not by the righteous law of God, but by their own good pleasure, consulting their own appetites instead of submitting to salutary restraint; also that they are carnal, and savour of death, and other such charges, which if he had uttered against even one servant of God, who would listen to him, who would not be bound to turn away from him? But now, when he assails with such reproachful and abusive language the Church bearing fruit and increasing throughout the whole world, and in almost all places observing no fast on the seventh day of the week, I warn him, whoever he is, to beware. For in wishing to conceal from me his name, you plainly showed your unwillingness that I should judge him.
Source: Letters (New Advent)