Then Judah said to Tamar, his daughter-in-law, “Remain a widow at your father’s house until Shelah my son grows up.” For he thought, “He may die also, just as his brothers did.” So Tamar went and lived in her father’s house.
But Onan knew that the descendant would not be his, so when he had relations with his brother’s wife, he let his semen go on the ground, so that he would not give a descendant to his brother.
If brothers dwell together, and one of them dies without having had a child, the wife of the deceased may not marry outside the family to a stranger. Her husband’s brother must go to her and take her to himself as a wife and perform the duty of a husband’s brother to her.
Turn back, my daughters! Go, for I am too old to have a husband. Even if I thought that there was still hope for me, that I could have a husband tonight and give birth to sons,