Adultery is, at minimum, unchastity within marriage, a violation of the marital vow of sexual exclusivity or fidelity.

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Adultery in Scripture

Commands about Adultery

Other Thoughts in Scripture about Adultery

Reflections about Adultery

Form of pollution

Theologically, adultery is a form of pollution or defilement. (Pollution, along with perversion and disintegration, are prime examples of corruption.) To pollute an entity is to introduce a foreign element into it, thereby weakening it. Idolatry pollutes our relationship to God and adultery our relationship to our spouse. The book of Hosea suggests strongly that idolatry and adultery are emblems of each other. Each introduces a rival into an exclusive relationship.

Form of injustice

1 Corinthians 7:4 states that married people have conjugal rights, suggesting that adultery, besides all else, is a form of injustice. Each partner has exclusive sexual rights to the other; adultery violates those rights.


All sin is equally wrong, but not all sin is equally bad. Acts are either right or wrong, either consonant with God's will or not. But, according to both Protestant and Catholic confessions, among right acts some are better than others and among wrong acts some are worse than others. Following Jesus' teaching in Matthew 5:27-28, Christians believe that fantasizing about adultery is just as wrong as committing it and not a different offense in kind. But Christians also know that adultery in one's heart damages others less, at least for the short term, than does adultery in a motel room and may therefore rank as less serious on the badness spectrum.

Inciting Unchastity

In Q&A 111, the Heidelberg Catechism makes a move common to many Protestant and Catholic confessions: It interprets adultery more broadly than a married person's sexual intercourse with someone other than his or her spouse. The Catechism interprets the commandment "Do not commit adultery" as forbidding all unchastity, whether in marriage or not, and, further, everything that incites unchastity, "whether it be actions, looks, talk, thoughts, or desires." Here, of course, Christians will want to indict the multibillion-dollar pornography industry, whose very purpose is to make big money by inciting unchastity.

In his searching study titled "Sex for Christians," Lewis Smedes makes the case for creative, whole-person fidelity within marriage, a kind of mutual enthusiasm for the other person's good. In this picture, adultery isn't just genital contact with persons outside the marriage. It's the introduction of any rival to the spouse's good. Workaholism or some other addiction, constant outings with buddies, emotional coldness, continuous griping — anything that gets in between the two spouses and blocks enthusiasm for the other's good qualifies as a kind of adultery, even if it is non-sexual.