Genesis 38:8

Then Judah said to Onan, 'Lie with your brother's wife and fulfill your duty to her as a brother-in-law to produce offspring for your brother.'

(New International Version)

Then Judah said to Onan, 'Go in to your brother's wife, and perform your duty as a brother-in-law to her, and raise up offspring for your brother.'

(New American Standard Bible)

And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother.

(King James Version)