Who does it, that is, with a bad conscience. And so if you should force him, and he should eat, there would be nothing gained. For it is not the eating that makes unclean, but the intention with which a man eats. If then thou dost not set that aright, you have done all to no purpose, and hast made things worse: for thinking a thing unclean is not so bad as tasting it when one thinks it unclean. Here then you are committing two errors, one by increasing his prejudice through your quarrelsomeness, and another by getting him to taste of what is unclean. And so, as long as you do not persuade him, do not force him.
Ver. 21. “It is good neither to eat flesh, nor to drink wine, nor anything whereby your brother stumbles, or is offended, or is made weak.”
Again, he requires the greater alternative, that they should not only not force him, but even condescend to him. For he often did this himself also, as when he circumcised, when he was shorn, when he sacrificed that Jewish sacrifice.. And he does not say to the man “do so,” but he states it in the form of a sentiment to prevent again making the other, the weaker man, too listless. And what are his words? “It is good not to eat flesh.” And why do I say flesh? If it be wine, or any other thing of the sort besides, which gives offense, refrain. For nothing is so important as your brother's salvation. And this Christ shows us, since He came from Heaven, and suffered all that He went through, for our sakes. And let me beg you to observe, how he also drives it home upon the other, by the words “stumbles, or is offended, or is made weak.” And do not tell me (he means) that he is so without reason but, that you have power to set it right. For the other has a sufficient claim to be helped in his weakness, and to you this were no loss, not being a case of hypocrisy, but of edification and economy. For if you force him, he is at once destroyed, and will condemn you, and fortify himself the more in not eating. But if you condescend to him, then he will love you, and will not suspect you as a teacher, and you will afterwards gain the power of sowing imperceptibly in him the right views. But if he once hate you, then you have closed the entrance for your reasoning. Do not then compel him, but even yourself refrain for his sake, not refraining from it as unclean, but because he is offended, and he will love you the more. So Paul also advises when he says, “It is good not to eat flesh,” not because it was unclean, but because the brother is offended and is weak.
Ver. 22. “Have you faith? Have it to yourself.”
Here he seems to me to be giving a gentle warning to the more advanced on the score of vanity. And what he says is this, Do you wish to show me that you are perfect, and fully furnished? Do not show it to me, but let your conscience suffice. And by faith, he here means that concerned not with doctrines, but with the subject in hand. For of the former it says, “With the mouth confession is made unto salvation”; and, “Whosoever shall deny Me before men, him will I also deny.” For the former by not being confessed, ruins us; and so does this by being confessed unseasonably. “Happy is he that condemns not himself in the thing which he allows.” Again he strikes at the weaker one, and gives him (i.e. the stronger) a sufficient crown, in that of his conscience. Even if no man see, that is, you are able to be happy in yourself. For after saying, “Have it to yourself,” to prevent his thinking this a contemptible tribunal, he tells him this is better to you than the world. And if all accuse you, and thou condemn not yourself, and your conscience lay no charge against you, you are happy. But this is a statement he did not make to apply to any person whatever. For there are many that condemn not themselves, and yet are great transgressors: and these are the most miserable of men. But he still keeps to the subject in hand.
Ver. 23. “And he that doubts is condemned if he eat.”
Again, it is to exhort him to spare the weaker, that he says this. For what good is it if he eat in doubt, and condemn himself? For I approve of him, who both eats, and does it not with doubting. See how he induces him not to eating only, but to eating with a good conscience too. Then he mentions likewise the reason why he is condemned continuing in these words,
“Because he eats not of faith.” Not because it is unclean, but because it is not of faith. For he did not believe that it is clean, but though unclean he touched it. But by this he shows them also what great harm they do by compelling men, and not persuading them, to touch things which had hitherto appeared unclean to them, that for this at all events they might leave rebuking. “For whatsoever is not of faith is sin.” For when a person does not feel sure, nor believe that a thing is clean, how can he do else than sin? Now all these things have been spoken by Paul of the subject in hand, not of everything. And observe what care he takes not to offend any; and he had said before, “If your brother be grieved with your meat, now you do not walk charitably.” But if one should not grieve him, much less ought one to give him offense. And again, “For meat destroy not the work of God.” For if it were a grievous act of iniquity to throw down a Church, much more so is it to do so to the spiritual Temple. Since a man is more dignified than a Church: for it was not for walls that Christ died, but for these temples.
Source: Homilies on Romans (New Advent)