And then there is nothing sweeter than a married husband and wife who share the same faith, which calls upon God with one voice. Each one is a mighty bulwark for the other when the faith of one is concerned for the other and labors on the other’s behalf in the presence of God. Finally, marriage is the sort of society of which Christ says, “Wherever two are gathered in My name, I am in the midst of them” [Matt. 18:20]. In true faith spouses should call upon God together, talk with each other about the Gospel, and teach the Gospel to their children. In the common life and perils of such spouses, Jesus Christ, the Son of God, is no doubt present and destroys the works of the devil, who, even as he strives to destroy the whole Church, directs his fiercest attacks against pious spouses and pious households. Amid all these dangers, however, the faith of the saints shines forth and Christ triumphs.
Martin Luther, Luther’s Works, American Edition, ed. Christopher Boyd Brown. vol. 60, Prefaces II, (Saint Louis: CPH, 2011) 272-73.