Genesis 38:9 – Onan, spilled seed, and levirate marriage
- May 1, 2025
- Posted by: Michael Hallett
- Category: Parables

Genesis 38:9, the story of Onan spilling his seed on the ground, is one of those Bible tales that many people know, yet don’t necessarily know its context.
Judah, one of the twelve sons of Jacob, had three sons: Er, Onan, and Shelah. Er married Tamar; however, “Er was very evil and the Lord took his life. So Judah told Onan, ‘It’s your duty to marry Tamar and have a child for your brother.’” (Genesis 38:7-8, Contemporary English Version)
We don’t know the nature of Er’s “evil” or how he lost his life, but we do know why Judah instructed Onan to marry Tamar: because of the custom of levirate marriage.
Levirate marriage
Levirate marriage is a traditional custom that requires the brother of a deceased man to marry his brother’s childless widow. It has historically been widely practiced around the world. The name derives from the Latin lēvir, ‘husband’s brother,’ and has nothing to do with the Book of Leviticus or the tribe of Levi.
The Judaic form of levirate marriage was called yibbum and is no longer practiced. Both parties had a right of refusal (known as halizah).
Judah’s instruction to Onan—that it’s his “duty”—suggests refusal was once seen as shameful. Non-performance of duty is always shameful; halizah involves a ritual which looks like a ceremonial absolution of shame.
Levirate marriage generally seems to be accompanied by three further stipulations:
- The demand falls on the surviving brothers in order of seniority;
- Any children are deemed to be children of the dead brother; and
- The children acquire their dead father’s inheritance rights.
Onan spills his seed
All three of these stipulations play a part in the unfolding story:
“Onan knew the child would not be his, and when he had sex with Tamar, he made sure she would not get pregnant.” (Genesis 38:9, CEV) The much blunter King James Version states that “when he went in unto his brother’s wife, that he spilled it on the ground, lest that he should give seed to his brother.”
Onan’s intent seems to have been to deceive Tamar (and Judah) into thinking he was doing his duty, but to retain inheritance rights stemming from his elder brother dying childless. Unfortunately for Onan, God was watching on one of those big screens in heaven (as He is wont to do) “and took his life too.”
Onan’s story might have disappeared into the musty recesses of Genesis. It became well known in the 18thand 19th centuries when ‘Onanism’ was the byword for an anti-masturbation craze that swept the western world.
While Protestant reformer John Calvin and Methodism founder John Wesley believed that masturbation was spiritually damaging, books like Onania, or, the Heinous Sin of Self-Pollution, and all its Frightful Consequences (In Both Sexes) Consider’d (1730, author unknown) claimed that self-pleasuring was also physically detrimental.
This whipped up a storm of anti-Onanistic sentiment that led, among other things, to John Harvey Kellogg inventing a breakfast cereal to take our minds off such activities.
“Be fruitful and increase”
Yet this is not what Genesis 38:9 is about. It’s all to do with birth rates.
While levirate marriage has pretty much died out, as recently as World War II it was revived in Central Asia when there were “shaky economic conditions.” (Wikipedia)
While Wikipedia connects levirate marriage with patriarchy, it doesn’t make the leap to recognise that patriarchal societies emerged as a survival mechanism during an age of long-term drought, desertification, and famine.
This means patriarchal laws and customs were designed to maximise a tribe’s chances of survival. Behind every law or custom, no matter how seemingly arbitrary, there was a logical, survival-based driver.
The Contemporary English Version of the Bible dates Onan’s story to around 1000 BC. This was a time of constant warfare, i.e., of high adult male mortality. The effect of this was a sizable group of young widows. The purpose of levirate marriage was for childless widows to help the tribe “Be fruitful and increase in number.” (Genesis 1:28)
Consequently, to be childless was a source of shame, as Rachel makes clear to Jacob in Genesis 30:1: “I’ll die if you don’t give me some children.” After giving birth to Joseph, she says, “God has taken away my disgrace.” (Genesis 30:23)
Judah and Tamar
The remainder of Genesis 38—the story of Judah and Tamar—is about taking away the disgrace of childlessness.
Judah tells Tamar, “Go home to your father and live there as a widow until my son Shelah is grown.” (Genesis 38:11) Tamar obeys. But Judah doesn’t keep his end of the bargain, presumably fearing the same will happen to Shelah. (There is no mention of a halizah.) Tamar dresses as a prostitute, tricks Judah, and later gives birth to twin boys.
Placed just before Joseph’s resistance to seduction by Potiphar’s wife in Genesis 39, Genesis 38:9 is easily interpreted as a sexual morality tale. Yet the reality of early patriarchal times was that tribes needed young men above anything.
Genesis 38 tells us that, sometimes, two wrongs can make a right. The wrongs were Onan spilling his seed, and Judah having sex with his daughter-in-law. Tamar forced Judah to rescue her from disgrace—and just as well.
As Jonathan Kirsch points out in The Harlot by the Side of the Road: Forbidden Tales of the Bible, “the coupling of the virile Judah and the fecund Tamar will bring forth the greatest kings of ancient Israel and ultimately the Messiah.”
Photo by zelle duda on Unsplash