Genesis 38:6-8

Young's Literal Translation

⁶ And Judah taketh a wife for Er, his first-born, and her name [is] Tamar;

⁷ and Er, Judah's first-born, is evil in the eyes of Jehovah, and Jehovah doth put him to death.

⁸ And Judah saith to Onan, `Go in unto the wife of thy brother, and marry her, and raise up seed to thy brother;'