Hebrews 13:4

Let marriage be had in honor among all, and let the bed be undefiled: for fornicators and adulterers God will judge.

The moral status of fornication and adultery is one; both are sinful. No technical difference deriving from the marital status of one or the other or both of the participants in such a sin can make any difference at all. Both sins alike, however they may be distinguished as different, are condemned; and they are treated in this verse as one in guilt and penalty. For more on this subject see under "Fornication" (Hebrews 12:16).

Many of the ancients translated this place as a declaration that "marriage is honorable in all," thus making it a declaration of the rights of all to enter the marriage state. The judgment of most modern scholars is reflected in the rendition given above, making it an exhortation that all should honor the marriage state. The teaching, however, leads to the same conclusion as in the old versions; for one may not lawfully depreciate the marriage state and contradict its holiness and sanctity by deeming it a contamination in some, such as priests, or by imputing to it any less holiness than pertains to any other lawful condition.