Luther’s Teachings on Marriage, Love, and Sex
We now turn from looking at the Luther’s marriage itself to offering a cursory review of Martin Luther’s teachings on marriage. A comprehensive treatment would make for a very large volume, so we will only scratch the surface of Luther’s rich teaching on these issues.
The Necessity of Marriage
Luther once asked a very simple but provocative question: “Why should one not forestall immorality by means of marriage?” Luther believed in the gift of celibacy—in fact, God granted it to him for many years. Paul had been granted the gift, and commended it in 1 Corinthians 7 as a blessing for the furtherance of the kingdom. But Luther also believed that it was a very rare gift. He suggested that many young men and women without the divine gift of celibacy were rejecting the divine gift of marriage. His counsel was that if you are struggling with lust, then your duty is simple: get married!
Whoever finds himself unsuited to the celibate life should see to it right away that he has something to do and to work at; then let him strike out in God’s name and get married. A young man should marry at the age of twenty at the latest, a young woman at fifteen to eighteen; that’s when they are still in good health and best suited for marriage.
Obviously the specifics here were not to be written in stone. After all, Katie was 26 and Luther was in his 41 years old when they were married! Further, this is not meant to be a discouragement for those earnestly desiring to marry. But it is an exhortation to those who are practicing what Albert Mohler has called “extended adolescence.” Mohler comments on the troubling trend of the “marginalization of marriage” in the church and world today:
Demographic trends, cultural shifts, and a weakening of the biblical concept of marriage have produced a situation in which marriage is in big trouble, even among many Christians. . . . By any calculation, the statistics indicate that young adults are marrying much later in life than at any time in recent human history. As a matter of fact, demographers have suggested that this new pattern of delay in marriage has established a statistical pattern that in previous generations had been most closely associated with social crises like war and natural disaster.
“From Genesis to Revelation,” Mohler writes, “the Bible assumes that marriage is normative for human beings.” Marriage is biblically normative. Therefore, it should be both expected and sought. Luther’s counsel is both blunt and necessary:
If you have the gift of abstinence and can live without sex, well and good. Then abstain from sex life. But if you cannot without sin abstain from uniting with a woman, then make use of the remedy God points out to you.
Luther’s words could not be any more relevant for the current crisis that Mohler identifies.
The Essence and Purpose of Marriage
Luther defined marriage in this way:
Marriage is the God-appointed and legitimate union of man and woman in the hope of having children or at least for the purpose of avoiding fornication and sin and living to the glory of God. 
And here is how he identified the purpose of marriage:
The ultimate purpose is to obey God, to find aid and counsel against sin; to call upon God; to seek, love, and educate children for the glory of God; to live with one’s wife in the fear of God and to bear the cross; but if there are no children, nevertheless to live with one’s wife in contentment; and to avoid all lewdness with others.
We see a number of important elements in this definition. First, its ultimate purpose is the glory of God. Second, we see that children are not just the blessed byproducts of marriage; they are part of the very essence of the marital design. I will have more to say on this below. Third, sanctification is at the very heart of marriage. Marriage is a God-appointed means of obeying God, fulfilling our God-given desires, avoiding sin, and instructing children in the faith.
Marriage Is an Instrument of Sanctification
One of Luther’s early metaphors for marriage was that of a hospital. “The temptation of the flesh has become so strong and consuming that marriage may be likened to a hospital for incurables which prevents inmates from falling into graver sins.” Roland Bainton notes that:
After his own marriage Luther’s tone shifted to a stress upon the home as a school for character. It is the area where the Christian virtues find their readiest exemplification, and, whereas in Catholicism monasticism is the sphere for the cultivation of the counsels of perfection, in Protestantism the home is as it were a functional substitute.
Both metaphors—a school and a hospital—signal the importance role of marriage as an agent of sanctification and rehabilitation. Our selfishness and pride are exposed. And if we respond in God-honoring humility, marriage can be used by God to cleanse us of our sin. The shift away from the monastic metaphor is also significant, for it signifies that marriage is never a purely private affair. Christian marriage is not to be of the world, but it must certainly be in the world. This leads to our next point.
Marriage Is Not a Sacrament
One of Luther’s most significant teachings was that marriage is not a sacrament. The tradition of viewing marriage as a sacrament was due in part to a mistranslation of the Latin Vulgate, which rendered mysterion (lit., mystery) as sacrementum in Ephesians 5:32. Luther argued instead that marriage was a public, civic matter: “Marriage is a civic matter (res politica). It is really not, together with all its circumstances, the business of the church. It is so only when a matter of conscience is involved.” As Lazareth summarizes: “Marriage is a wonderful blessing of God but it is not a Christian sacrament. . . . Marriage is still under the law of God but not under the wing of the church.” This does not in any way lessen the spiritual significance of marriage. As we saw above, Luther viewed marriage as a school for sanctification. But why relegate it to the civic realm? Because marriage is not designed only for Christians. It is a creation ordinance—a rule of God established for all people. Obviously we desire that all people bow their knees and acknowledge Jesus as their Lord—as all will do one day (Phil. 2:11). But that is not a prerequisite for a legitimate marriage. Marriage is not to be “regarded as a holy sacrament in the realm of grace, but honored rather as a divine ordinance in the realm of creation.” Marriage, therefore, is designed as an institution to serve the public good and is to thereby be the foundation for a well-ordered society.
Sex Is Good, Necessary, and Should Be Celebrated within Marriage
Against those who downplayed marriage, denigrated sex, and urged lifelong continence, Luther taught that unless one has the rare gift of celibacy, marriage and sex are both natural and necessary.
It is not a matter of free choice or decision but a natural and necessary thing, that whatever is a man must have a woman and whatever is a woman must have a man. . . . It is just as necessary as the fact that I am a man, and more necessary than sleeping and waking, eating and drinking, and emptying the bowels and bladder. . . . And wherever men try to resist this, it remains irresistible nonetheless and goes its way through fornication, adultery, and secret sins, for this is a matter of nature and not of choice.
In other words, God designed us as sexual beings, and this should lead the majority of us to seek sexual relations in a covenantal marital relationship comprised of one man and one woman.
Physical union between man and wife, however, is not a sufficient condition for a healthy marriage:
I have observed many married couples coming together in such great passion that they were ready to devour each other for love, but after a half year the one ran away from the other.
A bride is taken quickly; to love her for a lifetime is a quite a different matter. . . . For merely sleeping together [copula carnalis] will not do it alone; there must also be unity and harmony of mind, habits, and life. Each must be patient and helpful with the other for things cannot always go smoothly.
Sex by itself can do nothing. There must also be a union of the heart and mind. In fact, sex in marriage can be overdone:
It is indeed true that sexual intercourse in marriage should be moderate, to extinguish the burning of the flesh. Just as we should observe moderation in eating and drinking, so pious couples should refrain from indulging their flesh too much.
Luther also wrote that “Intercourse is never without sin,” which has led some to imagine that he thought the sex act was inherently evil. This conclusion, however, ignores the qualification that Luther immediately adds:
Intercourse is never without sin; but God excuses it by his grace because the estate of marriage is his work, and he preserves in and through the sin all that good which he implanted and blessed in marriage.
So there is sin bound up with the sex act, but marriage is the matrix for the redemption of sex. Allan Carlson comments on this passage: “Through marriage, sex became a moral good, an expression of God’s will. This was the heart of Luther’s sexual revolution.” It is also important to note that Luther extolled the virtues and beauty of pre-Fall sex:
[T]ruly in all nature there was no activity more excellent and more admirable than procreation. After the proclamation of the name of God it is the most important activity Adam and Eve in the state of innocence could carry on—as free from sin in doing this as they were in praising God.
But the Fall introduced disastrous results:
If Adam had not fallen, the love of bride and groom would have been the loveliest thing. Now this love is not pure either, for admittedly a married partner desires to have the other, yet each seeks to satisfy his desire with the other, and it is this desire which corrupts this kind of love. Therefore, the married state is now no longer pure and free from sin.
In sum, then, we see that Luther praised the virtues of pre-Fall sex, sees marriage as the matrix of redemption for sexuality, and yet still sees the sin lurking in the marital bed. If all we knew was the above, then we might conclude that Luther had a low—or at least a reserved—view of sex and its place in the Christian life. But Luther was also an advocate for celebrating the gift of sexual union. When Luther’s longtime correspondent Spalatin got married just five months after Martin and Katie, Luther wrote him a note, obviously delighted that his friend would be able to experience the joy of sex with his new bride. Heiko Oberman notes that this “erotic passage” “was stricken from editions of Luther’s letters very early on.”
When you sleep with your Catherine and embrace her, you should think: “This child of man, this creature of God has been given to me by my Christ. May he be praised and glorified.” On the evening of the day on which, according to my calculations, you will receive this, I shall make love to my Catherine while you make love to yours, and thus we will be united in love.
Furthermore, in accordance with Scripture (1 Cor. 7:3-5), Luther celebrated the idea of regular sexual intercourse within the bounds of marriage. Whereas the apostle Paul’s counsel was only in general, unspecified terms, Luther was more than happy to give specific detail! William Lazareth writes: “As to the recommend frequency of marital coitus, the hale and hearty spirit (if not the actual words) of Luther’s sexual counsel is reflected in the humorous couplet traditionally ascribed to him: “Twice a week, hundred-four a year, should give neither cause to fear.”
We see then in Luther a healthy, joyful appreciation for the gift of sex in marriage. Lazareth summarizes Luther’s view: “Christians who have been transformed by the gospel are not to avoid sex, but to dedicate their sexual gifts—like all others—both joyfully and shamelessly to the glory and service of God.” Finally, Lazareth rightly captures Luther’s view of marriage, family, and sex with the following description: “Luther’s faith was simple enough to trust that after a conscientious day’s labor, a Christian father could come home and eat his sausage, drink his beer, play his flute, sing with his children, and make love to his wife—all to the glory of God!”
 Albert Mohler, “Looking Back at the Mystery of Marriage: Part One,” http://www.crosswalk.com/news/weblogs/mohler/?adate=8/19/2004 (accessed 1/19/05). Time Magazine recently ran a coverstory (Jan. 16, 2004), entitled “Grow Up? Not So Fast,” observing that “This isn't just a trend, a temporary fad or a generational hiccup. This is a much larger phenomenon, of a different kind and a different order. Social scientists are starting to realize that a permanent shift has taken place in the way we live our lives.” See http://www.time.com/time/covers/1101050124/story.html (accessed 1/19/05).
 Roland H. Bainton, What Christianity Says About Sex, Love and Marriage (New York: Association Press, 1957), 79.
 LW 45:49.
 Allen C. Carlson, “A Revolutionary Theology of Sex: Martin Luther on Sex, Marriage and Family,” Witherspoon Lectures (July 2, 2004), http://www.witherspoonfellowship.org/index.cfm?get=item&b=7&item=WT04G01# (accessed 1-14-05).