[aMorePerfectUnion]

It is a sin to have intentionally barren intercourse.

Chapter and verse please, Mrs. Don-o?

[Mrs. Don-o]

I already gave you Genesis 38; plus the whole survey of Scripture where fertile sex is blessed, and intentionally infertile sex of any sort is never, never, ever blessed.

Not seeing that is like the Footprint Scene in Godzilla 1998 (worth a click) where the "worm guy" can't see the footprint because it's all around him: he's standing in the middle of it.

The rest is Natural Law Philosophy, for which you can find libraries full. It recognizes that normal, natural human sexuality is in itself a created good. Therefore to directly intend and choose to disable a healthy system is unethical, for the same reason that sex reassignment surgery is unethical: it is acting directly against a natural good.

And who said it was a good? Surely God.

And explicitly defining what that means, in terms of the sanctity of sex, is a development of doctrine which has been there since Genesis, and was embraced by all Christians until-- comparatively speaking --- 15 minutes ago.

[Salvation]

God said, “Go forth and multiply.”