Large Catechism: Marriage Praised & Honored (LC I 199-210)

But this commandment is aimed directly at the state of marriage and gives us an opportunity to speak about it. First, understand and mark well how gloriously God honors and praises this estate. For by His commandment He both approves and guards it. He has approved it above in the Fourth Commandment, “Honor your father and your mother.” But here He has (as we said) hedged it about and protected it. Therefore, He also wishes us to honor it and to maintain and govern it as a divine and blessed estate because, in the first place, He has instituted it before all others. He created man and woman separately, as is clear. This was not for lewdness, but so that they might live together in marriage, be fruitful, bear children, and nourish and train them to honor God. (206-207)