Genesis 38:8 YLT

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;'

⁹  and Onan knoweth that the seed is not 'reckoned' his; and it hath come to pass, if he hath gone in unto his brother's wife, that he hath destroyed 'it' to the earth, so as not to give seed to his brother;

¹⁰  and that which he hath done is evil in the eyes of Jehovah, and He putteth him also to death.