“If two brothers live together, and one of them dies without a son, the wife of the dead man must not marry a stranger outside the family. Her husband’s brother must take her as his wife and have sexual relations with her. He must do the duty of a husband’s brother for her.
Then Judah said to his daughter-in-law Tamar, “Go back to your father’s house. Stay there and don’t marry until my young son Shelah grows up.” Judah was afraid that Shelah would also be killed like his brothers. So Tamar went back to her father’s home.
Go back home. I am too old to have a new husband. Even if I thought I could be married again, I could not help you. If I became pregnant tonight and had two sons,
Onan knew that the children from this union would not belong to him. He had sexual relations with Tamar, but he did not allow himself to stay inside her.