“How far is too far?” That’s what the middle-school and high-school boys I taught used to ask me where it came to their interactions with girls. And the men who first listened to Jesus’ Sermon on the Mount were no different. In the seventh commandment, God had clearly said “Thou shalt not commit adultery” (Exodus 20:14), thus absolutely forbidding sexual relations outside the bonds of marriage. But they sought some wiggle room, just as we modern people do: if it’s not okay to touch, want’s wrong with a look? And if marriage is required before satisfying your carnal urges, then why not change husbands or wives whenever you want?

But Jesus will have none of this sort of self-centered approach to human sexual behavior. In fact, in this passage, He challenges so many of the Romantic notions that have become so popular since the middle of the 19th Century. For Jesus insists that we must pursue not only purity of action but of thought and emotion. And He makes it clear that marriage vows are intended to be permanent, not disposable whenever our whims or feelings change.

But why are Jesus’ teachings so strange to our modern ears? Simply because we have confused lust and love. Lust, after all, is focused on the self, on our own happiness and fulfillment. And that means that the sort of Romantic love that hungers for the beloved so that the beloved can satisfy or complete the self is really nothing more than self-centered lust, no matter how carefully we might try to idealize or rationalize it.

In contrast, true love is most clearly demonstrated on the cross of Christ. For there, the Lord gave Himself up for His bride, the Church, in spite of the fact that the people for whom He died had despised and rejected Him. On the cross, because of His true love, Jesus gave us not what we deserve but what we need, in spite of the tremendous cost to Himself. True love is therefore relentlessly determined to bless the beloved, while lust is only concerned with securing blessings for the self.

I think that’s why Jesus includes verses 29 and 30 in the midst of today’s passage: for in order for us modern people to recover a Biblical view of sex and marriage, we must be willing to discard not just our fondest Romantic notions, but also our dearest desires for our own happiness. For it is only in disinterested, self-sacrificial giving that we can ever hope to bless those who are closest to us. And that’s the only way any of us can ever truly follow Jesus.

Matthew 5:27-32 (NASB)

27 “You have heard that it was said, ‘You shall not commit adultery’;
28 but I say to you, that everyone who looks on a woman to lust for her has committed adultery with her already in his heart.
29 “And if your right eye makes you stumble, tear it out, and throw it from you; for it is better for you that one of the parts of your body perish, than for your whole body to be thrown into hell.
30 “And if your right hand makes you stumble, cut it off, and throw it from you; for it is better for you that one of the parts of your body perish, than for your whole body to go into hell.
31 “And it was said, ‘Whoever sends his wife away, let him give her a certificate of divorce’;
32 but I say to you that everyone who divorces his wife, except for the cause of unchastity, makes her commit adultery; and whoever marries a divorced woman commits adultery.