“Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body.”
The Apostle Paul really doesn’t want the ancient Corinthians to be sexually immoral. He uses the word, porneia, which used to be translated by the old word, fornication. It means all sexual activity outside of marriage. In his impassioned plea to flee it, Paul makes a curious categorization. Every other sin you could commit is outside the body, he says. But sexual sin is in a class by itself. It is an offence against (or into) one’s own body.
What does he mean? When we lie, we also do that in our bodies and with our bodies. When we steal, we are also using our bodies wrongly. We are denying what is true and offending God. So why would sexual sin be somehow worse?
It is because of the importance of our bodies, really the sexual identity of our bodies. In sexual sin, we are assaulting the image of God in us. Lying and stealing are bad, but fornication, sex outside of a marriage, is a visual, physical assault against the image of God.
Do you ever wonder about the strange importance of the Second Commandment, about not making false images of God? “Thou Shalt Not Make a Graven Image (of Me).” That is, whatever you might put up and say, “this is like God,” a bird or an animal or a sunset, is very false. Yes, they may express some quality of God in a limited way, but not really God. So, says Moses, you might as well not even try. God has given us a unique image of Himself—It is men and women in relationship (Genesis 1:27).
When you have sex outside of a strong covenant you are assaulting the picture of God in the world in a unique way. That covenant is dire. Its commitment is not only life-long. It is all-of-life consuming. It is a loyalty above other loyalties. It is blood-letting. It is becoming one.
In marital sex we are being shown the consuming commitment of God within Themself. To smash that picture, as happens in fornication, is to lose the crucial element of love: sole commitment.
You see, life is a really a struggle to believe that God really is Who He is. When the principal image is smashed, it further obscures what is already harder for us to grasp, that God is Love. With every act of fornication, it becomes a little harder to believe that He really loves us, because we are no longer seeing the way the Trinity is with Each Other. So Paul contrasts, in the sentence just before, being with a prostitute with being with the Lord (v17). How you are with another intimately has a lot to do with how you understand God with you.
And thus Paul asks next: don’t you know that your body is a temple of the Holy Spirit, that is, God’s presence proclaiming the love between the Father and the Son (v19)? Expressing the union of the Triune Persons is what human bodies in relationship were created to convey.
Do you know that about yourself?