What Jesus taught about murder in the Sermon on the Mount (Matthew 5) he now teaches in a directly parallel way about adultery. He defines it first, teaching that lust or any other impure sexual thoughts are the equivalent of adultery, just as anger or scornful talk is the equivalent of murder. Then he teaches what can be done about it, saying that whatever causes a person trouble in this area should be dealt with radically.

Is adultery wrong? Yes, that is what Jesus teaches. Is sex outside of marriage wrong? Yes, that is clear too. But Jesus is not just picking on people who have fallen into open sexual sins, as so many in our day have. He is probing deeper into the meaning of this commandment, and what He is saying is that the root of the problem is in the impure desires of the heart. It is there, in the heart, that something is radically wrong.

In Mere Christianity, C. S. Lewis is discussing ethics and comes to the Bible’s teaching about sex. He says that the appetite is in ludicrous excess of its function. Then he illustrates: “You can get a large audience together for a strip-tease act—that is, to watch a girl undress on the stage. Now suppose you came to a country where you could fill a theater by simply bringing a covered plate onto the stage and then slowly lifting the cover so as to let everyone see, just before the lights went out, that it contained a mutton chop or a bit of bacon, would you not think that in that country something had gone wrong with the appetite for food? And would not anyone who had grown up in a different world think there was something equally queer about the state of the sex instinct among us?”

The common argument against this idea is that sex is a problem but that it has become so only because it has been hushed up, as the Victorians are supposed to have done. But that was a century ago. In our day sex and sex-related matters are not hushed up. Nor have they been hushed up for decades. They are discussed without end on the internet, in magazines, radio, television, not to mention their treatment in movies. Yet we have more outright perversions, more adultery, more divorce, more illegitimacy, and more downright misery and confusion in this area than at any time in our history. Hushed up? As Lewis says, it is probably the other way around. People hushed up sex originally because it had become such a cesspool.

In the meantime, what should be done? I suppose Jesus was thinking of people living in an age such as ours when he prescribed the radical treatment described in Matthew 5. As many people know, these verses led the early church father Origen to obey them literally by having himself castrated. This is not what Jesus is teaching here. The meaning is this: Get rid of whatever is tempting you to sin. Pornography (for help please visit www.covenanteyes.com; (877) 705-7796), movies. Get rid of the poison. Protect your mind from such defilement.

Of course, in the final analysis, the answer to the problem is not merely to escape the temptation, especially today when it is nearly impossible to avoid all perverse sexual stimulation by our culture. The real answer is a biblical understanding of marriage and of joyful sexual experience within it. But that is something developed elsewhere in the New Testament.

Another problem with marriage among the Jews in Jesus’ day was the ease with which so many men divorced their wives. How could this happen in a culture so deliberately based on the Bible and its standards? Or among a people known for being so centered on the family? The answer is what we have been saying all along: the perversion of the heart. In the case of divorce, it worked like this also.

The only passage in the Old Testament to deal explicitly with divorce was Deuteronomy 24.1-4. The passage does not teach divorce, though it recognizes that it happens, stating that husbands should give their wives formal divorce certificates to indicate they had renounced all claim to them. The point of the passage is that if a woman has been divorced by her husband, marries another man, and is then released from that marriage either by another divorce or by the second husband’s death, then she is not allowed to return to the first husband on the grounds that “she has been defiled.”

But here is what happened. In exactly the way people often function in moral areas today, the teachers of Christ’s time had become legalistic about the “certificate of divorce” but excessively liberal about what the husband was allowed to find “displeasing” or “indecent” in his wife. They ignored the matter of remarrying the first husband entirely.

Defining what was displeasing led to a well-known disagreement between the Rabbis Shammai and Hillel. Shammai was a conservative, and he interpreted the grounds of offense as adultery or sexual impurity in the woman. Hillel was a liberal, and he broadened the woman’s offense to include even so trivial matters as spoiling dinner, being troublesome or given to quarrels, or speaking disrespectfully of her husband’s parents. Given the nature of the human heart, it is easy to see which interpretation prevailed. Divorce was allowed for nearly anything.

Hendriksen says, “The more we study Christ’s teaching as presented to us in this passage the more we begin to appreciate it. Here, by means of a few simple words, Jesus discourages divorce, refutes the rabbinical misinterpretation of the law, reaffirms the law’s true meaning, censures the guilty party, defends the innocent, and throughout it all upholds the sacredness and inviolability of the marriage bond as ordained by God!”