The Real Sin of Onan
I was a teenage new believer the first time I heard someone talk about the “sin of Onan.” The message was clear—and honestly, kind of terrifying: don’t masturbate. God killed a guy for it once.
That story, told in Genesis 38, got repeated in various youth group talks and church settings. Onan became shorthand for what not to do with your body when you’re alone. His name was a warning: “Don’t be like Onan.” Touch yourself like that and God might just touch you to kill you.
But when I actually read the passage, I found that it doesn’t say what I was told it says.
An Old Reading That Misses the Point
It’s true that for centuries—especially in medieval Roman Catholic tradition—this passage was interpreted as a condemnation of any “spilling of seed.” The act of ejaculation outside the context of procreation, whether through withdrawal or masturbation, was viewed as inherently sinful. That interpretation shaped a lot of what was passed down in purity culture, and it’s still influencing the way some churches talk about sexuality today.
But here’s the problem: the story in Genesis 38 isn’t about that. Not really.
The passage doesn’t focus on the physical act itself. The emphasis is on something much deeper—and far more disturbing.
A Story of Injustice and Power
Here’s what actually happens.
Judah’s son Er marries Tamar, but Er is wicked and dies without children. In that culture, the responsibility fell to the next brother—Onan—to marry the widow and give her a child in his brother’s name. That child would carry on the family line, receive the inheritance, and secure Tamar’s place in the family. It wasn’t just a formality; it was a matter of honor, security, and justice.
Onan agrees outwardly. He sleeps with her. But he makes sure she never conceives. Every time they have sex, he interrupts it—instead ejaculating on the ground.
Why? Because he knew the child wouldn’t be his.
And so he used her body while denying her the dignity, protection, and future that should have come with that union. He trapped her in a kind of sexual slavery—reaping the pleasure but withholding the promise. There was no way forward for her. No way out.
That’s the sin of Onan.
And God saw it.
And He acted.
God's response makes it clear what he thought. This injustice was wicked and Onan was put to death.
It Wasn’t Just Onan
As disturbing as that part of the story is, what follows might be even harder to stomach. Because when Onan dies, Judah makes a promise to Tamar: that she’ll marry his youngest son when he’s older. But the text makes it clear—Judah never had any intention of following through. It was a way to make Tamar disappear. Out of sight, out of mind.
Judah didn’t want to take responsibility. He didn’t want to face what had happened in his own family, under his own roof. And rather than pursue justice for Tamar, he chose to preserve his own comfort.
How often do those with power act that way?
How often do we?
Tamar’s Bold Response
Eventually Tamar realizes no one is coming to rescue her. No one is going to step in and do what’s right. So she takes a drastic step. She disguises herself as a prostitute and waits for Judah on the road. When he sees her, he propositions her—not realizing who she is.
She uses his own appetites against him.
She asks for a pledge—his signet, his cord, and his staff. The ancient equivalent of handing over your wallet and driver’s license. And then she conceives.
When her pregnancy becomes obvious, Judah is enraged. He calls for her to be burned to death. The hypocrisy is stunning. He’s the one who used her. He’s the one who abandoned her. And now he’s the one demanding punishment?
Until she sends word: “The man who owns these is the father.”
And suddenly, Judah is confronted with the truth.
He says something remarkable: “She is more righteous than I.”
That moment—where his sin is laid bare—is a turning point. He’s confronted with the reality of his own behavior. The stuff he ignored, or minimized, so that he could continue to believe himself to be a man worthy of honor and respect is now open and public.
He’s humbled. Confronted. And changed.
What This Story Is Really About
The story of Onan isn’t about masturbation. It’s about the abuse of power. It’s about a man who used someone weaker than him for his own gain and denied her the justice she deserved.
It’s about a father who enabled that injustice by refusing to act.
And it’s about a woman who had no legal recourse, no protector, and no future—until she forced the truth into the light.
This isn’t a purity culture fable. It’s a warning about what happens when those with power choose self-preservation over justice. When people get used for pleasure and discarded when they become inconvenient. When injustice gets swept under the rug because dealing with it would cost too much.
The sin of Onan wasn’t private or personal. It was relational, systemic, and cruel.
So What Do We Do With This?
If we want to avoid Onan’s sin—and Judah’s—we need more than good sexual ethics. We need the courage to look at how our decisions (or indecisions) affect those with less power than us. We need to ask whether our convenience is coming at the cost of someone else’s dignity. We need to pay attention to the invisible Tamars in our lives.
And maybe most of all, we need the humility to admit when we’ve been wrong—and to let that moment of truth change us.
Because justice matters to God.
Even in the messy stories.
Even in the shadows.
And to those who, like Tamar, are living in the shadows of the abuse of power, know that God will not withhold your justice forever.
Here's something really cool. Jesus comes from the line of Judah. He is a direct descendant of this broken and repentant man.
But you want to know what's more cool than that? Matthew lists only five women in his genealogy and guess who one of them is?
That's right. Tamar.
One of Judah's sons would eventually be the messiah, and it would come through the line of Tamar. They denied Tamar her dignity, but God didn't. They robbed Tamar of her legacy, but God restored it with astounding glory.
Tamar, the great-great-great (who knows how many greats) - grandmother of Jesus was vindicated by Jesus. Not just because he was her descendant, either. Yes, that was a great honor.
Jesus didn't just come from Tamar. He came for her. And for every other outcast and outsider in need of justice, forgiveness, and restoration to God's love.
Jesus, a descendant of Judah, did not repeat Judah's sin. Instead of acting in the love of power for personal gain or pleasure, he acted in the power of love to stand with and for the marginalized, abused, and forsaken.
And the Onans of his day killed him for it.
Little did they know, though, that through his death (and resurrection), Jesus would bring ultimate justice and make life available to all. They exercised their selfish power to destroy, but God, in his wisdom, over-ruled their injustice with the greater power of love - to redeem and restore.
Yeah, so in a world of Onans, I think it's a good idea to try to stand with the Tamars.
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