Genesis 38:9

Genesis 38:9, in plain English

Onan sleeps with Tamar but deliberately avoids fathering a child, spilling his seed on the ground so she won't conceive.

Why it's here

Onan understands the law—he knows that any child born would legally belong to Er, not to him. He'd be supporting a son who wouldn't inherit from him or carry his name. So he uses Tamar for pleasure while refusing to give her what she desperately needs. He's selfish and cruel.

Who's speaking

The narrator, explaining Onan's deliberate action

Where it sits in the story

This shows you what happens when someone refuses to honor their obligations, even when it costs someone else everything. Onan's refusal to protect a vulnerable woman reveals his character, and it foreshadows how Judah will soon do something similar—and worse.

The scholarly reading

Onan deliberately practices a form of contraception, spilling his seed on the ground, because he knows any children produced would legally belong to his brother Er rather than to himself.

Language and setting

The Hebrew וַיְשַׁמַּר (vayshammer, 'he guarded/protected') suggests conscious, deliberate action. What scholars call onanism (from Onan's name) is here explicitly motivated by property law and inheritance—not by mere lust or perversity, as later Christian moral theology sometimes interpreted it. Onan's sin is fundamentally one of covenantal refusal: he benefits from marital relations but refuses the obligation to produce an heir for his brother. This is an act of familial betrayal masquerading as self-preservation.

Voice

The omniscient narrator of Genesis

Significance

Onan's refusal to honor the levirate duty becomes the catalyst for Tamar's taking justice into her own hands—his failure of obligation makes her later initiative morally intelligible and ultimately vindicates her.

7But Er, Judah’s firstborn, was wicked in the sight of the LORD; so the LORD put him to death.

8Then Judah said to Onan, “Sleep with your brother’s wife. Perform your duty as her brother-in-law and raise up offspring for your brother.”

9But Onan knew that the offspring would not belong to him; so whenever he would sleep with his brother’s wife, he would spill his seed on the ground so that he would not produce offspring for his brother.

10What he did was wicked in the sight of the LORD, so He put Onan to death as well.

11Then Judah said to his daughter-in-law Tamar, “Live as a widow in your father’s house until my son Shelah grows up.” For he thought, “He may die too, like his brothers.” So Tamar went to live in her father’s house.

Read all of Genesis 38 — A strange detour from Joseph's story. Judah's failures and Tamar's boldness both play a role in the ancestry of the Messiah.