I've been around here [this post was originally drafted for r/TrueChristian] for a long time, and this question keeps coming up from a variety of angles. I think I actually end up writing this post about once every couple years because the issue never quite goes away.

You want to know why sexual sin is sin? Because we were designed to reflect God's image to the world and to Him. If you can understand the way our physical lives reflect a spiritual truth about God and how he relates with his people, many mysteries of Scripture suddenly make sense - especially the correlation between the old and new testaments.

For the sake of this post, let's stick to two of the most discussed aspects of sexual sin: homosexuality and masturbation.


Physical Parallels the Spiritual

Throughout all of the Bible we see that humanity's function is to reflect God's image to the world and even to Himself. This is how God is glorified. But there is a gap between the spiritual God we serve and the physical world we live in. When humanity was young, it could not understand the spiritual things of God, so God gave us physical, tangible examples to help us understand who he is and what he expects of us.

  • Physical circumcision was a symbol of what God would do in our hearts (Romans 2:28-29)

  • A nation of Abraham's physical descendants was a symbol for the spiritual nation God was building (Romans 9:8)

  • Marriages between men and women were a symbol of the spiritual marriage Christ would have with his Church (Ephesians 5:32)

  • Relationships between fathers and their children were a symbol of the spiritual relationship between our Father and us, his children (1 Cor. 4:15)

When the fall happened, humanity stopped reflecting God's image as intended. But God's intent for us to reflect his image remained. God never stopped calling his people to holiness, nor has he stopped his efforts toward sanctifying us.

In short, anything that breaks the image of Himself that God intended to reflect through our lives is sin. The call to sanctification and holiness is a restoration of that image. God's actions on the physical world - especially as expressed through the Old Testament - are an effort to show us through physical things we could understand the spiritual truths that we otherwise couldn't. It's not surprising, then, that Jesus often spoke in parables, using physical things God created to help us understand spiritual things we were otherwise ignorant about. And he also spoke stories from the Old Testament not for the mere purpose of communicating a moral, but to demonstrate that God was using those historical events as a foreshadow of the spiritual realities that were coming into place with the cross - and indeed were always in place, but were not understood until after the veil was torn.


The Sexual Image We Bear

Insofar as it pertains to sexuality, God's design for humanity is that we would be his children and a spiritual lineage would flow throughout the world from beginning to end, through Him, which we call evangelism (causing someone to be "born again") and discipleship (raising a child to maturity). From the beginning of creation itself, God made his expectations known: "Be fruitful and multiply." God created life first, and then told mankind to do the same thing, living in his image.

Bizarrely, most people assume that this was a command to produce physical offspring. Adam and Eve did just that. They produced lots of offspring. Some people estimate there could have been as many as trillions of people on the planet at the time of the flood. Even conservative estimates are much higher than the present global population. Yet God did send a flood to wipe them all away, expressing to the world, "That's not what I meant when I told you to fill the world." In Malachi 2:15 he clarifies, "And why did the Lord God make them [husband and wife] one, with a portion of his Spirit in their union? To produce godly offspring." The pre-flood population missed the "godly" part. God didn't merely want warm bodies across the earth; he wanted spiritual life, not embodied death (Romans 7:24).

In reading Ephesians 5, it's almost impossible to miss the parallel Paul says God intended between physical marriage and the relationship Christ has with his church. Jesus even refers to himself as the bridegroom, and Revelation makes clear that we are his bride. This includes the reproductive and child-raising nature of marriage, as is evident through the ways Scripture talks about how spiritual life is born from the union between God and his people - that this oneness bond is what produces fruit flowing from our lives. It's almost impossible to miss this when we read Acts 1:8 - that when the Holy Spirit comes on us, indwelling within us, we will become God's witnesses. To what end? That people be born again.


Broken Image 1: Masturbation

The Cultural Position

God's design for sexuality was that it would be used as a vehicle to help us understand the imperative for spiritual reproduction today. Have you ever been bewildered by the cultural difference between the Old Testament and today on having children? If you didn't have children back then, you were shamed and cursed. If you were a woman with a closed womb, it was as if your life had no meaning. If you were a man with a dysfunctional penis, you were prohibited from entering God's assembly. Having children - and lots of them! - seemed to be the highest pursuit for virtually everyone in those days, and we see numerous women pleading with God for children or becoming embittered when they don't have them. A woman's success and virtue was defined by her ability to birth children for her husband.

This is a cultural imperative that we simply miss today, and I believe there are at least two reasons for this - one good, another ... not so much.

First, we have direct access to the spiritual truth that the physical parallels are meant to point to. As such, we don't need the physical example anymore. The road map matters very little when you're already at your destination. Though if you wander off, it's nice to have it to guide you back again. When we are already producing spiritual generations from our life, we have no imperative toward producing physical children. This is perfectly appropriate.

The second is more significant because very few people are actually spiritually reproducing the way Jesus modeled. If not the first, then the alternative reason society doesn't have the same interest in mass-child-rearing as biblical societies did is that they're not reflecting God's image properly. Society has developed a view that children are a wonderful blessing when you feel ready, but that it's perfectly normal and acceptable to decide not to have kids as well.

This isn't surprising in the age of pornography and mass-acceptance of masturbation. Even into the 50s it was an ideal to have several children playing behind your white picket fence. But as masturbation rose, sexuality became less about reproduction and more about pleasure. This ultimately manifested in 1967, when states began permitting no-fault divorce, which had the impact of treating not only sexuality, but marriage itself (an inherently sexual relationship) as a vehicle for individual happiness. This continued through the 70, which laid the groundwork for the sexual revolution, opening the sexual marketplace to anyone, anywhere, at any time, as long as they both wanted it. There were no longer legal repercussions. Needless to say, this degraded the integrity of the family unit itself, initiating a stark rise in divorce rates that have had the trend of increasing ever since.

We could have a chicken and egg debate over whether pornography and masturbation caused the sexual revolution, or if it was a byproduct of the revolution that allowed for its mass-monetization. I lean toward the former. But the correlation cannot be missed.

The Spiritual Implication

Let me be clear: I'm all on-board with the idea that sex is fun and should be enjoyed between a husband and wife as often as they feel. What I'm trying to hone in on, though, is the modern self-indulgent view of sexuality. Consider how this is similar to the way average churchgoers view spiritual reproduction.

  • I often hear people coming back from mission trips talking not about how many people were saved, but about how much fun they had on the trip.

  • I constantly hear Christians get all excited about having shared the Gospel with someone - and their focus is on how good it made them feel, rather than on the fact that the person they shared with still rejected them and went to hell.

  • Sunday services where the Gospel is preached have become a vehicle for mass-entertainment to keep the people in the seats pleased.

But let's get to the real meat of this parallel: the fact that actual reproduction is impossible through masturbation. That's ultimately why it's sin.

We are meant to be a reproducing people. This was God's first command to Adam and Even in Genesis 1:28, it was Christ's last command before he ascended in Matthew 28:19-20, and it's the imperative when the Holy Spirit comes on us in Acts 1:8. Our reproductive efforts are always designed in Scripture to be expressed with another person. God doesn't model mass-reproduction by himself the way you'd think if we looked at a porn addict as bearing God's image, right? Instead, God works through the Church, his bride.

When we masturbate, we communicate to the world that we don't need God or that God doesn't need us. That is, a husband can be satisfied by himself without his bride, and a bride can be satisfied on her own without her groom. It communicates that spiritual reproduction (evangelism) is about our own pleasure and that we should be able to experience that pleasure without needing God in the mix and without any actual intent to make a convert - just to feel good about ourselves.

Moreover: if husbands, specifically, reflect Christ's groomship to his bride, the Church, and we physically masturbate, then this communicates to the world that God, on a spiritual level, masturbates. What does that even mean? I assume it means that he gets off on the idea of spreading his Gospel to new believers without any actual intent of drawing anyone to himself. And yet we know this is a false image of God because the Bible says that God wants to draw all people to himself and is not desirous that any should perish.

I'm sure you can ponder many more ways that masturbation within marriage disassociates from the type of relationship Christ wants to have with his bride. Feel free to leave them in the comments.


Broken Image 2: Homosexuality

What we do with our marriages and children communicates something to the world about the type of relationship Christ wants with his bride or the Father wants with his children. We are always reflecting something about God through the way we live.

  • If a husband is abusive toward his wife, it reflects to the world that Christ will be abusive toward his bride, the Church. This is a false image. 1 John 4 says that Jesus doesn't punish us and Jeremiah 29:11 says God's plans are not to harm us.

  • If a wife decides it's okay to cheat on her husband, this communicates through her behaviors that it's okay for the Church to cheat on Christ from time to time. This is a false image. The first command is to have no other gods before our God, and the Bible is repetitively clear that we are not to cheat on him with idols, using the whole book of Hosea to verify the sexual parallel between a spouse cheating on her husband and God's people cheating on him.

  • If a wife is lazy and does nothing but watch TV all day, expecting her husband to do everything by himself, this communicates that it's okay for the church to be lazy and expect Jesus to do everything for us. This is a false image. Jesus didn't say, "Sit back and watch me take the Gospel to the nations." He delegated that responsibility to us.

Similarly:

  • If two men "marry," they are communicating to the world that Christ has no place for the church - grooms are fine without a bride. This is a false image, as the Bible is clear that even though Christ doesn't need the church, he has still chosen the church to be his vehicle through which he would work.

  • If two women "marry," they are communicating that the church doesn't need Christ - that brides are fine without a groom. This is a false image, as the Bible is clear that the church has no value apart from Christ.

  • A homosexual couple cannot have children flowing from their relationship. If this is permitted, it presents to the world that it's perfectly acceptable for Christ or the church not to produce spiritual offspring either - that it's enough just to love each other. This is a false image in defiance of the great commission and what Jesus has said about what loving him looks like.

Additional Considerations:

Some people bring up adoption, which homosexual couples can do. But this is like saying Christ would produce spiritual offspring with someone other than the Church and then have the Church be the one to raise the baby. This is also a false image. Yes, God could have the stones cry out, as Scriptures say. But he doesn't do this because he is faithful to his church, which is also repeated throughout Scripture.

Others object that allegedly Christ wouldn't condemn a heterosexual marriage simply because one or the other was sterile and couldn't have kids, and therefore reproduction shouldn't be the qualifier of a marriage that reflects Christ's relationship with the church to the world. Otherwise a sterile person would be prohibited from ever marrying. There are several problems with this. The first and most obvious one is that this only accounts for the third bullet point I gave above and does nothing to address the first two (and more that I haven't listed).

More to the point, this confuses the road map with the destination. The physical example is the road map to help us understand the spiritual reality, which is the destination. A couple who is producing spiritual offspring through evangelism and discipleship has arrived at the destination and no longer needs the road map. Instead of reflecting a shadow, they are a beacon for the actual image itself - a spiritual lineage being what flows from the relationship rather than a physical one.

Additionally, while they may not have actual children, sterile couples engaging in sex are still demonstrating through their relations a type of intimacy that would ordinarily produce new life, but for the sterility. This is a healthy image because Christ's bride regularly engages in reproductive efforts without actual reproduction occurring - preaching the Gospel, but finding no converts. This is an affirmation of the pragmatic reality of the spiritual relationship we experience with Christ, and not a defiance of it. It appropriately acknowledges that not every spiritually reproductive effort will result in someone being born again - and that's okay. Homosexual sex, on the other hand, doesn't even bear a reproductive intent from the start. No gay man or lesbian has legitimately expected to conceive a baby from their relations.

In this context, it's also worth noting that God opens and closes wombs, so even a sterile couple can have sex with the hope or expectation that God can defy their sterility. There are biblical examples of this, so it's not an unreasonable thing to pray for or otherwise expect might happen, even in the absence of prayer. The possibility of conception is always there. No homosexual couple legitimately expects God to perform a miracle to get a man pregnant without a womb or that a woman would be inseminated through her bride's finger, and there are no biblical examples of God ever doing such a thing. The spiritual reality behind all of this is, of course, that when we share our faith through Christ, it's ultimately up to God whether or not someone is born again as a result. We don't see Christ sharing the Gospel with himself (masturbation) or with the Spirit (akin to male homosexuality) with no church or people around, expecting to produce a new convert. Nor is it in any way fruitful for Christians to evangelize each other (akin to female homosexuality). Of course, when Christians do attempt to evangelize each other, it's because they legitimately believe the other person isn't saved, but that's a separate can of worms.

Again, the point here is not whether or not someone is actually capable of having children, but in what is reflected to the world and to God by our physical interactions. Because of this, the significance is not in the technicalities of statistics and sterility (even if God couldn't do miracles), but in the fact that the world and God would perceive a couple putting forth reproductive effort and not finding success, much like many believers (Christ's bride) put forth spiritually reproductive effort and simply don't produce new life, as everyone they preach to turns the message down. This is consistent with God's reproductive intentions with the church. Even if a homosexual couple was misinformed enough to believe they could get each other pregnant through their actions, the world and God would still not have that image reflected to them; rather, they would simply see a couple that is either deluded or doesn't actually intend to produce offspring in the first place.

Further, there are several places in Scripture where people are made sterile by God to serve a purpose. That purpose often includes the fact that God is using the physical example of their sterility to show how someone can become spiritually sterile as well, and the impact that this should have on our relationship with Christ, our thoughts toward spiritual reproduction, and ultimately the dependence we have on Christ to birth new spiritual life through us rather than us thinking we can do it of our own power. In the case of homosexuals, all they are proving is that life cannot be produced in the absence of the church and Christ working together, which demonstrates that they are not modeling a Christ/church relationship, and therefore are not legitimately married or living up to the image of marriage God expects.

Remember: the Bible says on at least two separate occasions that the one who fails to produce good fruit will be chopped down and thrown into the fire. It doesn't say the one who produces bad fruit; but the one who fails to produce good fruit. This is significant. Fruit is the offspring of a tree - Jesus is talking about disciples as the fruit. Homosexual couples cannot produce good fruit, much less any fruit at all, and therefore it doesn't matter how much we may otherwise think they are good people - and I know some who I love dearly.


CONCLUSION

Sex can certainly be enjoyed between a husband and wife, even if it doesn't result in conception. But everything we do reflects on our Father and Groom. If we act inconsistently in our own marriages with the way Christ intends to relate with us in our communal spiritual marriage to him, we reflect a broken image to the world of who God is and how he intends to relate with his people, which is a hindrance to the Gospel being spread throughout all nations.

The framework here is not one of hating homosexuals or people who masturbate; rather, it is that engaging in these types of behaviors is entirely inconsistent with the spiritual purposes God has had for his people since the creation of the world, and we should not tell lies through our behaviors about God. Actions speak louder than words.

I say this to a community of predominantly straight people not to echo-chamber the same dogmatic principles that often get talked about anyway, but to a background and understanding to the issue that can create empathy through understanding why these matters are sin, rather than the standard Bible-thumping approach. When my kids don't understand my rules, they will obey me when I tell them, "Because I said so!" But that phrase does nothing to help them understand me and know me better. Sometimes they're too young to grasp the rationale behind my rules, but as soon as they are capable of receiving it, suddenly they empathize and are even far more likely to obey and to love their siblings when they falter, rather than tattling for the rule's own sake.