Romans 14:14 - Matthew Poole's English Annotations on the Holy Bible

Here he obviates an objection. Some might say, they were thoroughly persuaded, that no meat was unclean in itself, and therefore they might, and would, use their liberty in eating any thing that was before them. To this the apostle answers, first, by way of concession; he grants what they say is true, and tells them, that for his own part he knew it full well, and was himself assured of it; and that he had this assurance from the Lord Jesus; i.e. that he was instructed therein by his word and Spirit. That there is nothing unclean of itself; i.e. that no meat was unclean in itself; it was not so in its own nature: see Genesis 1:31, Genesis 9:3. Some creatures might be unwholesome, but none were in themselves unclean: to the Jews they were not unclean by nature, but by a positive law, which law was now antiquated and out of doors: see Colossians 2:16,17 1 Timothy 4:3,4. But to him that esteemeth any thing to be unclean, to him it is unclean: this he adds by way of restriction, that though no meat was unclean in itself, yet it was so to him that thought it to be unclean. If a man shall believe that there is yet a difference in meats, that some are still unclean, and that by virtue of God's prohibition, it would be evil in him to eat such meats, because he therein acts against his conscience, and doth that which he himself thinks to be a sin: see Romans 14:23.