John Calvin Commentary 1 Corinthians 6:13

"Meats for the belly, and the belly for meats: but God shall bring to nought both it and them. But the body is not for fornication, but for the Lord; and the Lord for the body:" — 1 Corinthians 6:13 (ASV)

Meats for the belly, and the belly for meats. Here he shows what use should be made of outward things—for the necessity of the present life, which passes away quickly as a shadow, consistent with what he says later (1 Corinthians 7:29). The principle is also that we must use this world so as not to abuse it.

From this, too, we infer how improper it is for a Christian to contend for outward things. When a dispute, therefore, arises concerning corruptible things, a pious mind will not anxiously dwell on these matters, for liberty is one thing—the use of it is another. This statement accords with another—that

The kingdom of God is not meat and drink (Romans 14:17).

Now the body is not for fornication. Having mentioned the exceptions, he now states further that our liberty should not by any means be extended to fornication. For fornication was an evil so prevalent at that time that it seemed almost as though it were permitted.

This can also be seen from the decree of the Apostles (Acts 15:20), where, in prohibiting the Gentiles from fornication, they placed it among things indifferent. There can be no doubt that this was done because it was very generally regarded as lawful.

Therefore, Paul now says there is a difference between fornication and meats, for the Lord has not ordained the body for fornication as he has ordained the belly for meats. And this he confirms from contrasting principles: the body is consecrated to Christ, and it is impossible for Christ to be joined with fornication.

What he adds—and the Lord for the body—is significant. For since God the Father has united us to his Son, what wickedness it would be to tear our body away from that sacred connection and give it over to things unworthy of Christ.