Christians don’t talk about sex.  We argue about it.  Loudly.  We make headlines.  And we convince just about everybody that we have nothing helpful to say about sex to anybody.
What a shame!
Sex is important stuff.  It’s powerful and life-shaping.  You would think that a religion that claims to make sense of all of life would have something crucial to say about sex.
As it turns out, Jesus himself gives us the definitive teaching about sex. 
In our rush to define the permissibility of the who, the what, the when and the where of physical sex acts, we’ve been too busy to linger for long on something more basic.  Jesus teaches us about why God made us sexual beings in the first place.

Here’s what Jesus says:
“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 they are no longer two, but one flesh.  (Mark 10:7-8; see also Matthew 19:5)
Drawing on Genesis 2:24, Jesus teaches us that sex is about becoming one flesh.  If Jesus were simply referring to the fact of physical intimacy, this would be uninteresting.
In order to hear Jesus more clearly, give this a try.  Instead of saying, “become one flesh,” substitute the phrase “joined at the hip.”  The two shall be joined at the hip.
When we have sex with each other, we become joined at the hip.
Wait a minute!
We use “joined at the hip” when we’re referring to soul mates.  Right? That term should be reserved for deeply intimate relationships.  We’re talking a deep spiritual bond here: two people so compatible that they finish each other’s thoughts, not to mention their sentences.  Right?
Nope.  I’m sticking with Jesus’ teaching on this one (and every one, actually).  It may be that the very term “soul mate” reveals where we’ve gotten mixed up about sex.
Some think that sex is just a physical appetite, like hunger.  If you’re hungry, then you eat.  If you’re sexually aroused, you have sex.  

From this perspective, sex is just a bodily function.  We can be physically involved and withhold our souls.  People make too much of a fuss about sex.  I once heard an older, very experienced priest say, “God doesn’t care where we put our *%#!#.”
This point of view suggests that God is only interested in our souls.  Our bodies pass away.  One glad morning our soul will fly away.  It will accomplish the prison break from the body and will fly up to heaven.  
This is not what Christians teach.  God became incarnate.  In Jesus he took on human flesh.  After he died he rose again: bodily.  We care about the sick, the hungry and suffering.  That’s because their bodies matter, just as much as their souls.
The body is, as it were, the skin of the soul. 
We are not souls trapped in a body.  We are a combination of soul and body.  And this brings us back to sex.
What we do with our body we do with our soul.  When we have sex with someone, we start to be joined at the hip.
Jesus underscores the inseparability of body and soul by reversing the order of things in the Sermon on the Mount.  He says:
“You have heard that it was said, `You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lust has already committed adultery with her in his heart.”  (Matt. 5:27-28)
In other words, what we do with our soul anticipates what we do with our body.  When we dwell on someone else as our sexual object, we begin joining ourselves to him or her at the hip.
Sex, as it turns out, is a way giving ourselves away with remarkable abandon.  We cannot decide to make it something else.  We may tell ourselves something different, of course.  But we’ll just be kidding ourselves.
Sex is God’s gift.  It’s one of the ways that we exercise Christ’s own way of life: giving ourselves away.  It changes who we are at our very core.
Maybe this will set aside a common misperception by non-Christians of what we Christians think about sex.  We’ve left the impression that we consider sex defiling and that we indulge in it only for procreation.
On the contrary, we think of sex as creating one of the most intimate, life-enhancing bonds we can imagine.  Sex unites us in body and soul.  God designed sex to form and to reinforce, over time, an enduring bond.
Does sex always actually happen this way? Of course not!  But it is God’s deep desire for us.  He wants us to know the joy of being joined at the hip.