Genesis 38:8-9

8Then Judah said to Onan, “Go in to ayour brother’s wife and bperform the duty of a brother-in-law to her, and raise up offspring for your brother.” 9But Onan knew that the offspring would not be his. So whenever he went in to his brother’s wife he would waste the semen on the ground, so as not to give offspring to his brother.
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