John Calvin Commentary 1 Corinthians 6:15

"Know ye not that your bodies are members of Christ? shall I then take away the members of Christ, and make them members of a harlot? God forbid." — 1 Corinthians 6:15 (ASV)

Know you not that our bodies are the members, etc. Here we have an explanation, or, if you prefer, an amplification of the previous statement. For that expression, the body is for the Lord, might, because of its brevity, be somewhat obscure. Therefore he says, as if to explain it, that Christ is joined with us and we with him in such a way that we become one body with him.

Accordingly, if I have relations with a harlot, I tear Christ in pieces, to the extent of my power; for it is impossible for me to draw Him into fellowship with such pollution. Now, since that must be held in abhorrence, he uses the expression he customarily employs in reference to things that are absurd — God forbid. Observe that the spiritual connection which we have with Christ belongs not merely to the soul but also to the body, so that we are flesh of his flesh, etc. (Ephesians 5:30). Otherwise, the hope of a resurrection would be weak if our connection were not of that nature — full and complete.