5 Augustine replied: Listen, and you shall hear what we mean and intend by quoting this verse against you, since you say that you do not know. It is not that you abstain from animal food; for, as you observe, our ancient fathers abstained from some kinds of food, not, however, as condemning them, but with a typical meaning, which you do not understand, and of which I have said already in this work all that appeared necessary. Besides, Christians, not heretics, but Catholics, in order to subdue the body, that the soul may be more humbled in prayer, abstain not only from animal food, but also from some vegetable productions, without, however, believing them to be unclean.
A few do this always; and at certain seasons or days, as in Lent, almost all, more or less, according to the choice or ability of individuals. You, on the other hand, deny that the creature is good, and call it unclean, saying that animals are made by the devil of the worst impurities in the substance of evil and so you reject them with horror, as being the most cruel and loathsome places of confinement of your god. You, as a concession, allow your followers, as distinct from the priests, to eat animal food; as the apostle allows, in certain cases, not marriage in the general sense, but the indulgence of passion in marriage. It is only sin which is thus made allowance for.
This is the feeling you have toward all animal food; you have learned it from your heresy, and you teach it to your followers. You make allowance for your followers, because, as I said before, they supply you with necessaries; but you grant them indulgence without saying that it is not sinful. For yourselves, you shun contact with this evil and impurity; and hence our reason for quoting this verse against you is found in the words of the apostle which follow those with which you end the quotation.
Perhaps it was for this reason that you left out the words, and then say that you do not know what we mean or intend by the quotation; for it suited you better to omit the account of our intention than to express it. For, after speaking of abstaining from meats, which God has created to be received with thanksgiving by believers, the apostle goes on, "And by them who know the truth; for every creature of God is good, and nothing to be refused, if it be received with thanksgiving: for it is sanctified by the word of God and prayer." This you deny; for your idea, and motive, and belief in abstaining from such food is, that they are not typically, but naturally, evil and impure.
In this assuredly you blaspheme the Creator; and in this is the doctrine of devils. You need not be surprised that, so long before the event, this prediction regarding you was made by the Holy Spirit.
Source: Reply to Faustus the Manichaean (New Advent)