Westminster Confession of Faith
Chapter 24: Of Marriage and Divorce
3: It is lawful for all sorts of people to marry, who are able with judgment to give their consent. Yet it is the duty of Christians to marry only in the Lord. And therefore such as profess the true reformed religion should not marry with infidels, papists, or other idolaters: neither should such as are godly be unequally yoked, by marrying with such as are notoriously wicked in their life, or maintain damnable heresies.