In Christian marriage, the husband and wife are called to be, first and foremost, the servants of one another. Admittedly such practical exhortations are not unique to Christian marriage. Indeed, in the last two chapters of Ephesians, Paul applies the exact same principles of love and mutual submission to virtually every relationship imaginable-man, woman, child, slave, and master. Nevertheless, the marriage relationship is unique in one sense. Let me explain.
Nothing shatters the illusion of our own decency quite like the intimacy of marriage.
No doubt this is why, in his first letter to the Thessalonians, Paul places his instructions regarding the marital covenant within the context of Christian sanctification. Now we ask you and urge you to do this more and more. But it does suggest that at least one of God's many purposes in marriage is the growth of the Christian believer. Martyn Lloyd-Jones, Studies on the Sermon on the Mount, Vol. See NIV footnote for variant reading.