What we do matters. This includes our bodies, our time, our interests. The example that Paul is talking about here is incest. You can twitter about this or that, but the pagans, who considered having boys as lovers OK, curled their toes up at that taboo. And the Corinthians had broken than boundary.

So… Paul tells the church to excommunicate him.

1 Corinthians 5:1-8

¹It is actually reported that there is sexual immorality among you, and of a kind that is not found even among pagans; for a man is living with his father’s wife. ²And you are arrogant! Should you not rather have mourned, so that he who has done this would have been removed from among you?

³For though absent in body, I am present in spirit; and as if present I have already pronounced judgment ⁴in the name of the Lord Jesus on the man who has done such a thing. When you are assembled, and my spirit is present with the power of our Lord Jesus, ⁵you are to hand this man over to Satan for the destruction of the flesh, so that his spirit may be saved in the day of the Lord.

⁶Your boasting is not a good thing. Do you not know that a little yeast leavens the whole batch of dough? ⁷Clean out the old yeast so that you may be a new batch, as you really are unleavened. For our paschal lamb, Christ, has been sacrificed. ⁸Therefore, let us celebrate the festival, not with the old yeast, the yeast of malice and evil, but with the unleavened bread of sincerity and truth.

The reason that we need to consider morality is quite selfish. Sexual immorality destroys us. If you are sleeping with a woman, you are not rational about that woman (unless you have ground the oneitis out of your system, and can no longer bond). This works both ways — for men and women. In marriage, this is a feature, for you associate her with the person you bonded to.

And the church remains pure. If the church tolerates impurity, it’s criticized — rightly — by the very world who expects the church to tolerate their sins.

And in the sexual realm, none of us are righteous.

Matthew 5:27-37

²⁷“You have heard that it was said, ‘You shall not commit adultery.’ ²⁸But I say to you that everyone who looks at a woman with lust has already committed adultery with her in his heart. ²⁹If your right eye causes you to sin, tear it out and throw it away; it is better for you to lose one of your members than for your whole body to be thrown into hell. ³⁰And if your right hand causes you to sin, cut it off and throw it away; it is better for you to lose one of your members than for your whole body to go into hell.

³¹“It was also said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’ ³²But I say to you that anyone who divorces his wife, except on the ground of unchastity, causes her to commit adultery; and whoever marries a divorced woman commits adultery.

³³“Again, you have heard that it was said to those of ancient times, ‘You shall not swear falsely, but carry out the vows you have made to the Lord.’ ³⁴But I say to you, Do not swear at all, either by heaven, for it is the throne of God, ³⁵or by the earth, for it is his footstool, or by Jerusalem, for it is the city of the great King. ³⁶And do not swear by your head, for you cannot make one hair white or black. ³⁷Let your word be &‘Yes, Yes’ or ‘No, No’; anything more than this comes from the evil one.”

On divorce (Speaking as one who has been there) the innocent party is allowed to remarry, if you follow reformed teaching, for the other party has acted, and you are allowed to live in peace. But divorce should not be casual. Nor should we cultivate lust (this is more than pornography, but links into modesty — women, men will desire you if you display publicly what should be shown but in your bedchamber, and yes, that is contextual).

But Christ linked this to your word. You have made a contract. It should not need to be elaborate. Your word — to have and hold, until death — should suffice, and for many years it did.

The gloss I would add is that it is in times of immorality that there are elaborate oaths and sexual witch hunts. (Consider the NSDAP with its elaborate pagan rituals and homosexual panic — despite a fair number of the leadership being as camp as J.Edgar)

In times of honour, the deviant are simply excluded from society: being caught has consequences. And in times of honour those who have difficulty with their sexuality are respected in their single state or their faithfulness despite their inclinations otherwise — from same sex attraction to the running a soft harem.

But these are not times of honour. So, in the church, we need to resurrect this — and our tolerance of immorality within the church is a scandal.