"I know, and am persuaded by the Lord Jesus, that there is nothing unclean of itself' but to him that esteemeth any thing to be unclean, to him it is unclean."
It is well to consider this entire chapter in its context. Paul was writing about a problem of judging among the apostolic believers. Verses 4, 10, and 13 exhort against the sin of judging one another. And it was true that a serious division existed in that early church. The Gentile Christians were judging the Jewish Christians, and the Jewish Christians were judging the Gentile Christians.
Notice how the previous verse strikes at the very heart of the issue. "Let us not therefore judge one another any more: but judge this rather, that no man put a stumblingblock or an occasion to fall in his brother's way." Verse 13.
What was the basis of the problem? Over what were they judging each other? The Gentiles who had come into the church from paganism were offended because the Jewish Christians ate food that had been offered in sacrifice to idols. And the Jewish Christians judged the Gentile church members because they had no regard for the ceremonial days that they still observed from Judaism.
Some of the Gentile converts were so fearful of eating meat offered to idols that they ate only vegetables. Paul spoke of them in verses 1 and 2. The Jewish Christians thought that was ridiculous and apparently made divisive attacks against their fellow Christians. It was so serious that Paul addressed the problem again in 1 Corinthians 8:8-12. There he elaborated at length on the "weak brother" (the Gentile believer) who esteemed the food unfit to be eaten.
What was Paul's counsel to the Jewish members who were judging the Gentile members? He told them not to eat the food offered to idols if they were in the presence of those who thought it to be wrong. Even though they had knowledge that the idol was nothing, he told the Jewish converts: "And through thy knowledge shall the weak brother perish for whom Christ died? But when ye sin so against the brethren, and wound their weak conscience, ye sin against Christ. 1 Corinthians 8:11, 12.
The food offered to idols was not unclean food (Acts 14:13), but was merely esteemed so by the Gentile converts. It was not a moral issue. Neither was the matter of the ceremonial days, which Paul mentioned in Romans 14:5. He told them to stop judging over those issues and to get on with the work. These matters had nothing to do with the moral questions of the seventh-day Sabbath and the forbidden unclean food.