Voyeurism

Scripture limits healthy, godly sexual relationships to those between a husband and wife. Any sexual relationship or activity that involves anyone other than a married couple is forbidden (Lev. 20). As the Bible defines it, "adultery" is a broad term encompassing sexual activity between non-married partners. That means that even if a married couple consents to have sex with another partner or partners, that activity constitutes adultery, as does simple one-on-one sexual activity with someone other than one's spouse. If a couple engages in a mΘnage a trios or group sex, both partners commit the sin of adultery with the extra person(s).

Sexual fantasies are also forbidden when the subject of the fantasy is sinful. Jesus taught that lusting after adultery violates the same commandment that committing adultery violates (Matt. 5:28; cf. Sexual Fantasy and Masturbation.

The Bible does not directly address the type of sexual activities permitted to a married couple. I believe it is rather permissive in this area. So long as the activity does not violate the commandments of Scripture, such as doing harm to one or both spouses (e.g., sadomasochism) or sinful fantasy, I believe the Bible permits it. I think that if all other activities than traditional vaginal intercourse were prohibited, the Bible would indicate this rather explicitly somewhere. After all, these activities have certainly been known in all ages and cultures. Scripture does permit spouses to "lie with" one another, and it is clear from some contexts that this and related terms may encompass a variety of activities (see Is Oral Sex a Sin?). I am not persuaded by traditional arguments against oral/anal sex (see Self Abuse?).