The 7th Commandment prohibits married people from having sex outside their covenant relationship. But this commandment is ultimately not about adultery; rather, it’s about marriage.
What does this law tell us about the Law-Giver? In Genesis, we read that God created humanity—male and female—in his divine image. Throughout Scripture, marriage is revered as an exclusive, legal, lifelong covenant between a man and a woman that forms the basis for the family. Later in the New Testament, the apostle Paul will declare that marriage is actually a picture of the mutual selflessness that characterizes the love that Christ and the Church have for one another.
God ordained the deep intimacy of marriage—expressed in the “one flesh mystery” of sex—as the setting where a husband and wife learn to give themselves fully to each other. The Holy Spirit uses the radical honesty and faithfulness required in marriage to transform our character. As we learn to live interdependently rather than insist on our own way, we become more Christ-like.
To give our body to another without also giving our life to them betrays that purpose and damages our capacity for oneness and Christ-likeness. Likewise, to break the marriage covenant by having sex with others violates the very trust and intimacy marriage is designed to create. The 7th Commandment not only guards the image of God as represented in marriage, it also protects husbands and wives from sabotaging their union. In spite of this, many of the Bible’s patriarchs were adulterers and polygamists; just as they were liars and swindlers. Their lives were just as in need of transformation as ours. Many people in Jesus’ day took self-righteous pride in the fact that they hadn’t technically committed the physical act of adultery. Much to their surprise, Christ tells them that those who lust are just as guilty as those engage in the act itself. He has good reason.
Fantasizing sexually about someone else is the first step toward adultery. Lust demeans those we objectify—those made in God’s image and redeemed by his Son. Lust makes us consumers trained to please ourselves. It creates unrealistic expectations about what a healthy relationship looks like. The danger (and allure) of lust is that it we can sin within our hearts and minds without anyone else—except God and us—knowing. Lust can be emotionally addictive and spiritually destructive. And it’s a way of life in our culture the same way it was in Jesus’ time.
That’s why Christ shocks us by commanding that we deal drastically with lust. He uses hyperbole when he tells us to pluck out our eyes or cut off our hands–making the point that we must go to any length to eliminate it’s power in our lives. Not managing it, but destroying it. Otherwise, the burning power of lust will consume and annihilate us. His warning is stern, but given with the love of a parent who wishes nothing but for his children to have healthy relationships with their fellow brothers and sisters, their spouse, and their Father in heaven.