John Chrysostom, on 1Cor 10:30

"If I by grace partake, why am I evil spoken of for that for which I give thanks?" "Of what dost thou 'by grace partake?' tell me." Of the gifts of God. For His grace is so great, as to render my soul unstained and above all pollution. For as the sun sending down his beams upon many spots of pollution, withdraws them again pure; so likewise and much more, we, living in the midst of the world remain pure, if we will, by how much the power we have is even greater than his.

"Why then abstain?" say you. Not as though I should become unclean, far from it; but for my brother's sake, and that I may not become a partaker with devils, and that I may not be judged by the unbeliever. For in this case it is no longer now the nature of the thing, but the disobedience and the friendship with devils which maketh me unclean, and the purpose of heart worketh the pollution. But what is, "why am I evil spoken of for that for which I give thanks?" "I, for my part" saith he "give thanks to God that He hath thus set me on high, and above the low estate of the Jews, so that from no quarter am I injured. But the Gentiles not knowing my high rule of life will suspect the contrary, and will say, 'Here are Christians indulging a taste for our customs; they are a kind of hypocrites, abusing the demons and loathing them, yet running to their tables; than which what can be more senseless? We conclude that not for truth's sake, but through ambition and love of power they have betaken themselves to this doctrine.' What folly then would it be that in respect of those things whereby I have been so benefited as even to give solemn thanks, in respect of these I should become the cause of evil-speaking?"

"But these things, even as it is," say you, "will the Gentile allege, when he seeth me not making enquiry." In no wise. For all things are not full of idol-sacrifices so that he should suspect this: nor dost thou thyself taste of them as idol-sacrifices. But not then scrupulous overmuch, nor again, on the other hand, when any say that it is an idol-sacrifice, do thou partake. For Christ gave thee grace and set thee on high and above all injury from that quarter, not that thou mightest be evil spoken of, nor that the circumstance which hath been such a gain to thee as to be matter of special thanksgiving, should so injure others as to make them even blaspheme.

"Nay, why," saith he, "do I not say to the Gentile, 'I eat, I am no wise injured, and I do not this as one in friendship with the demons'?" Because thou canst not persuade him, even though thou shouldest say it ten thousand times: weak as he is and hostile. For if thy brother hath not yet been persuaded by thee, much less the enemy and the Gentile. If he is possessed by his consciousness of the idol-sacrifice, much more the unbeliever. And besides, what occasion have we for so great trouble?