Exodus 20:14: “You shall not commit adultery. (ESV)
The command to not commit adultery is the second in a run of four commands in quick succession. They receive no commentary or exposition. This leaves it to the reader or hearer to properly interpret the meaning and scope of the command.
The Seventh Commandment in Its Time
This command prohibits adultery, which is understood to involve sexual relations with another person's spouse. It is interesting that the command does not prohibity sexual immorality of all kinds, but specifically targets one particular form of sexual immorality.
Why not forbid any sexual expression outside of marriage? Other commandments are broader in scope (e.g., you shall not murder, you shall not steal). Then again, some are more specific. Children are commanded to honor their fathers and mothers. And yet, the honor children should give to fathers and mothers is clearly part of a principle of submission and deference to authority in general. The command relates specifically to children with their parents, but that does not restrict all honor to that relationship. We could say that children's submission to and honoring of their parents is the base needed for proper relationships related to authority and honor in society. If children do not honor parents, what hope can there be for society?
We may draw a similar conclusion regarding the prohibition against adultery. It is not singling out one aspect of sexual immorality above the rest. The command sets the prohibition against adultery as a foundation on which to build a pure sexual morality for society as a whole. If spouses are not faithful to one another, everything else falls apart anyway.
Perhaps a key takeaway from the reasoning above is that the prohibition against adultery was never intended to serve as the bare minimum for sexual morality among God's people. If men and women gratified every distorted desire other than the specific act of adultery, would the commandment have been kept? That would be like saying children should honor their parents, but no other authority demands their obedience. Honor does not stop with parents. Rather, children learn the foundation for proper honor from their parents, which then influences the rest of their relationships in society.
It is better to read this prohibition against adultery more in terms of an iceberg than a single checkbox. In order for adultery to be avoided, illicit sexual desire must be put away. Personal habits which lead to the formation of illicit sexual desires must be dealt with. In order for adultery to be avoided, a whole alternative morality must be developed. And that is what this commandment requires. The prohibition is the tip of the iceberg. This single command brings with it an entire moral economy which must characterize the people of God.
This is why Paul can write to the Corinthians to flee sexual immorality altogether without batting an eye (1 Cor. 6:18). Why was this not viewed as extreme if the seventh commandment is restricted to adultery only? It is because God had already revealed his will as far back as Moses at Mount Sinai. Sexual expression is to be restricted to one's spouse. The marriage bed marks a boundary line which sexual expression may not cross and outside of which nothing else may enter. This is what it means for the marriage bed to remain undefiled (Heb. 13:4).
The Seventh Commandment Today
So how do we think about this commandment for us today? It is helpful to remember that Jesus himself addressed the issue while he was on earth. In the Sermon on the Mount, Jesus says that the commission of adultery is not just in the external act, but can also be committed in the heart (Matt. 5:27-28). To look at someone with lustful intent is to commit adultery in the heart.
Jesus sets a far higher standard than the seventh commandment would initially appear to set. But then, God has never been interested in mere outward conformity. God emphasized to his people throughout the centuries that the state of the heart toward him is what mattered most, and they understood that (cf. 1 Sam. 16:7; Ps. 7:9; Jer. 17:10; 1 Chron. 28:9). If anything, the mistake would be on the side of the interpreter who wants to see in this commandment a bare prohibition against adultery. The command is not less than a prohibition against adultery, but it is more than that. It is not that God is saying one thing and meaning another. The scope of the commandment is simple and rather narrow when first considered. But as the implications of the commandment are considered and taught, the scope grows broader and broader to encompass much more than might at first appear.
It is important for us today that we understand that moral purity does not consist in the avoidance of certain actions. Moral purity is not less than not committing adultery, but it is more. It appears to me that we are intent on restricting the commandments of God to the smallest possible area so that we can gratify our desires, at least partially, while still remaining faithful to God's commands.
But we do not need to inflate or read into the meaning and scope of God's commands either. It appears to me that the balance can be struck by faithful and diligent teaching. God's people in the Old Testament did not simply read the Law. They had and needed interpretation to tease out the different aspects of the Law along with its implications (cf. Ezra 7:10; 8:2-3, 8).
If we are going to live for God through Christ, we must take the prohibition against adultery seriously. It ought to be obvious that anything named in the Ten Commandments must be a very big deal. Our society loves "Top Ten" lists. The Ten Commandments are perhaps the original "Top Ten" list, and it comes from God himself.
What a commandment like this one does, especially given Jesus' teaching on it, is to press us to consider the state of our hearts before God. As we consider our own hearts, those who have never committed adultery find they are not so different from those who have. The same principle of sin is in our hearts as in theirs. What remains is not so much a fixation on avoiding adultery itself, but the downward slide that leads to it. And the way to correct the downward slide is by keeping our attention up, where Christ is, seated at the right hand of the Father, for there our life is hidden with Christ in God (Col. 3:1-3).