What is strictly forbidden in Scripture regarding marriage?

The belief that sexual involvement outside of marriage is strictly forbidden in Scripture is grounded in various biblical passages that emphasize the sanctity of marriage and the importance of fidelity. In many religious contexts, including Christianity, marriage is viewed as a covenant relationship designed by God, and any sexual relations outside of that covenant—commonly referred to as adultery—are considered a serious breach of this sacred union.

Biblical texts, such as Exodus 20:14 ("You shall not commit adultery") and Hebrews 13:4 ("Marriage should be honored by all, and the marriage bed kept pure, for God will judge the adulterer and all the sexually immoral"), underscore the expectation of sexual purity within marriage and the moral imperative against engaging in sexual acts outside of that commitment.

In contrast, the other choices reflect practices or concepts that are addressed within Scripture but do not carry the same level of explicit prohibition as sexual involvement outside of marriage. For example, while divorce is discouraged in many passages, it is permitted under certain circumstances, such as marital unfaithfulness, highlighting a distinction in how these concepts are treated scripturally. Co-habitation, while generally viewed negatively in many religious communities, is not explicitly mentioned in the same terms, and separation is addressed