Spanking bench/horse

It depends on the religion. Judaism is a highly legalistic religion in which every detail of observance is spelled out precisely. Anything that's not expressly forbidden is entirely acceptable. There are few gray areas. I have three orthodox cousins who happen to be lesbians. That isn't a problem. There is no Talmudic prohibition against women having sex with other women. But sex between men, on the other hand, is entirely prohibited at risk of lightning-bolt interruption. When I asked a rabbi why this was so, he shrugged and said: "Who every thought women would do such a thing?" Now there's a fine example of Abrahamic thinking. If there's no penis involved it isn't sex. Likewise, with BDSM, when I asked a rather renowned Talmudic scholar about it, he had to think it over, which involved a lot of rocking, beard stroking and mumbling before he grinned, pointed upward and pronounced: "There's no rule against it!" While there is a religious offshoot of the BDSM community that considers some mild "spousal discipline" (for women only of course) merely a natural extension of patriarchal primacy in marriage, I suspect most major religions would frown on BDSM engaged in for openly sexual reasons, though that may be the agenda of both partners. A little hypocrisy helps preserve the order of things. Overall, the association of BDSM and religion is historically problematic and couples who want both have to square the circle in their own ways.