The following is Russell Moore’s response, to the ethical question that he first posted:
Shortly after I posted this question, Candice Watters pointed me to the counsel of Christian scholar J. Budziszewski to a man ina very similar predicament. You can read his advice here. I agree almost entirely with his assessment.
Several factors bear on this decision. The first is that, yes, the Scriptures make it clear that Christian marriage is to be the union of a faithful man and a faithful woman. We are not to be, the Bible maintains, “unequally yoked with unbelievers” (2 Cor. 6:14). If you were merely dating this woman I would counsel you to immediately end the relationship. But the situation is, of course, more complicated than that.
The Apostle Paul, for instance, does not treat already existing marriages believer to unbeliever as an ongoing state of sin. Those who are already in this predicament should, Paul says, continue in it, unless the unbeliever abandons the marriage (1 Cor. 7:12-16).
Well, why? Wouldn’t it be better for one’s sanctification to be married to a godly spouse than to an unbelieving one? Sure. But divorcing one’s spouse, walking away from one’s vows and responsibilities would compound the sin, piling sin upon sin, in a way that furthers the damage already done. The Scriptures tell us not to “yoke” ourselves with unbelievers, true, but we are also not to abandon our responsibilities to the “yokes” we already have.
The question here is not whether you will be yoked unequally with an unbeliever. You are. The question is whether you can or should get out of it.
Read Dr. Moore’s response in full.