Romans 14:23

It is true that if someone thinks it wrong to eat but does so anyway, he is condemned. For he makes himself guilty when he does what he thinks he ought not to.If someone acts against his better judgment in a matter of conscience, then …

But he who makes a distinction, if he eats, is condemned, because it is not of faith. And everything that is not of faith is sin. He who makes a distinction in this way — that is, who doubts whether what he takes is truly clean or unclean — that man, from the very doubt of his own mind, is condemned by his accusing conscience. He also sets forth the cause of this condemnation, saying: Because it is not taken of faith, but assuredly out of doubt. And after these things he propounds a general sentence upon all things, saying: And everything that is not of faith is sin. By this word he binds with a tighter bond the negligent and slothful souls of any believers whatever, that they should do nothing without faith, say nothing apart from faith, nor think anything apart from faith: because whether you have done something without faith, or spoken, or even thought it, you sin. This is the same as what he says elsewhere: Whether you eat or drink, or whatever else you do, do all to the glory of God. But someone may ask whether the heretics too, in what they do, since they act according to what they believe, are to be held to act out of faith; or whether, because the faith among them is evil, everything they do is to be pronounced sin, since it is not done of faith. For my part, I think that their credulity is called faith rather than is faith. For just as false prophets are sometimes by a false name called prophets; and false knowledge is called knowledge; and false wisdom is by misuse named wisdom: so also the credulity of heretics is by a false name called faith. Whence it must be considered whether perhaps even if some good work seems to be performed among them, because it is not done of faith, it is turned into sin, as was said of a certain man: Let his prayer become sin. […]

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 eateth, and doeth 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 eateth 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 thy brother be grieved with thy meat, now walkest thou not charitably." But if one should not grieve him, much less ought one to give him offence. 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.

Every word or deed or thought which does not look to Christ looks completely to the adversary of Christ. For it is not possible for what is outside of light or life not to be completely in darkness or death.… The person outside of Christ rejects him by what he thinks, does or says.

As to those who are overtaken by an involuntary flux in the night-time, let such follow the testimony of their own conscience, and consider themselves as to whether they are doubtfully minded in this matter or not. And he that doubteth in the matter of …