It’s genesis 38, and a rather quick read if you’re that curious.

But the long and short of it is that Judah got his son, Er a wife, named Tamar. Er was “displeasing” or “evil in the sight of god”, so he got smote. That is, god killed him. Er had no heir, and in accordance with the time, she was married off the her brother-in-law Onan.

The idea being that Onan gets her pregnant and the son becomes Er’s heir. This provided Tamar with income since she would then manage her hypothetical son’s interests until he was of age.

Anyhow Onan wanted the inheritance for himself (he was next in line, and Judah was wealthy- the founding patriarch of the kingdom of Judah.)

So, he pulled out. (“Spilled his seed on the ground”.) so god offed him for being a greedy dick, too.

His third son was too young so Judah sent her back to her father, until he grew up (something that wasn’t honored.) so, one day Judah is going out to sheer some sheep, sees a prostitute and offers her a goat. The prostitute asks for collateral (his seal and some other stuff. A walking stick.); when Judah has a goat sent to the shrine for her, uh, service the messenger can’t find her and is told there’s no hookers.

A few months later, Judah is told Tamar is preggo, from prostitution, people want her stoned. So she goes before him and says she was never paid for sex, and therefore not a hooker; and that her child’s father gave her a seal. (Yup.)

The scripture did say that he didn’t do it again…(sure we believe you.)