The Sixth Commandment

Sermon for Midweek of Trinity 11

Small Catechism Review: The Sixth Commandment

The Fifth commandment taught us how God forbids us to dishonor human life with our thoughts, words, or deeds, and how He commands us to honor it. The Sixth Commandment teaches us how God forbids us to dishonor His institution of marriage with our thoughts, words, or deeds, and how He commands us to honor it.

You shall not commit adultery. What does this mean? We should fear and love God, that we lead a pure and chaste life in word and deed, and each one love and honor his spouse.

Just as there’s an obvious definition of murder, so there’s an obvious definition of adultery. It’s when a married person has sexual relations with someone other than his or her spouse. So, first and foremost, we’re talking about a husband’s sin against his wife or a wife’s sin against her husband by straying from the faithfulness they promised to each other when they took their marriage vows. We’re obviously also talking about the sin of the third party, the person with whom the husband or wife stepped outside of the marriage to commit sexual immorality.

We should say a few words about marriage before we go on. Scripture defines it as the joining of one man and one woman into a union that is to last “as long as they both shall live.” That union was established by God already in the Garden of Eden, when He presented the newly created Eve to the recently created Adam, and Adam declared, This is now bone of my bones and flesh of my flesh; she shall be called Woman, because she was taken out of Man.” Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh. And Jesus confirms that union, that oneness, when He says in Matthew 19, Have you not read that He who made them at the beginning ‘made them male and female,’ and said, ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh’? So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate.”

The “one flesh” of marriage applies to the whole earthly life of husband and wife, including the body. As Paul writes to the Corinthians, The wife does not have authority over her own body, but the husband does. And likewise the husband does not have authority over his own body, but the wife does. And that oneness is to last until husband or wife dies. In other words, God forbids divorce, except in the extreme situations of actual adultery or malicious desertion.

We can identify three purposes that God intended for marriage. Marriage is designed to provide lifelong companionship for husband and wife. It’s God’s divinely instituted means of bringing children into the world, to give them a stable home, with a mom and a dad, devoted to one another, who will raise their children to know and to fear the Lord. And marriage provides a divinely created means to preserve chastity.

What is chastity? It’s the godly discipline of reserving all sexual relations for the loving use of husband and wife. It’s very simple. God has placed sexual desires into men and women, and God has provided the context of marriage for fulling those desires. Marriage is to be the context for all sexual relations. Apart from marriage, God provides no context for any sexual relations. On the contrary, He forbids them.

Anything that threatens or disturbs the sacredness of marriage is also forbidden by God and summarized with the commandment, You shall not commit adultery. As it says in Hebrews 13, Marriage should be honored by all, and the marriage bed kept undefiled; but fornicators and adulterers God will judge. Now, the word “fornication” is a broad term in the Bible that applies to all sexual immorality, from sex between unmarried people, to indecent language and joking, to viewing pornography, to the sinful lust of the heart. Jesus clarified the Sixth Commandment for the Jews when He said, You have heard that it was said to those of old, ‘You shall not commit adultery.’ But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart. And Paul wrote to the Ephesians, But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints; neither filthiness, nor foolish talking, nor coarse jesting, which are not fitting, but rather giving of thanks.

Then we come to the crass forms of sexual deviancy like homosexuality, and all this chaos over “gender”—men pretending to be women, and women pretending to be men, or something else entirely. These, too, are forms of adultery which God condemns both in the Old and the New Testaments. They’re perversions of God’s creation and of God’s institution of marriage, and they are the death of a society when they’re openly embraced, as they now are in most societies of the world. The world cannot survive much longer.

On the positive side, what does it look like to “lead a pure and chaste life,” where “each one loves and honors his spouse”? It looks like fleeing from sexual immorality, as Paul puts it to the Corinthians. It looks like honoring marriage, as instituted by God, in our hearts, in our speech, and in our actions. It looks like seeking a godly spouse with prayer and sound judgment, putting God’s Word and the worship of God before everything else. And it looks like husbands and wives being devoted to one another, as Christ and His beloved Church are devoted to one another.

That’s the pattern of a Christian marriage, as Paul writes in Ephesians 5: Wives, submit to your own husbands, as to the Lord. For the husband is head of the wife, as also Christ is head of the church; and He is the Savior of the body. Therefore, just as the church is subject to Christ, so let the wives be to their own husbands in everything. Husbands, love your wives, just as Christ also loved the church and gave Himself for her…So husbands ought to love their own wives as their own bodies.

Where have you failed to keep this Sixth Commandment? Where have you failed to lead a pure and chaste life, in your thoughts, in your words, in your actions? Where have you failed to treat marriage as something sacred and honorable? The Sixth Commandment, like the rest, shows us our sin and condemns us in the courtroom of God’s justice.

Which is another reason why only a fool would plead his case before God on the basis of how well he has kept the Sixth Commandment. Our only plea must be, God, have mercy on me, a sinner, for the sake of Your Son, Jesus Christ, whose every thought, word, and deed were pure and chaste, who honored marriage and defended it in my place, and who suffered and died for my unchastity and loveless behavior! Then, clothed in Christ’s righteousness and having God’s forgiveness, let the Sixth Commandment guide you each day into the new obedience of God’s beloved children, to the glory of God and to the preservation of mutual love within marriage, and God-pleasing chastity within and without. Amen.