Then Judah said to Er’s brother Onan, “Go and have sexual relations with your dead brother’s wife. It is your duty to provide children for your brother in this way.”
But Onan knew that the children would not belong to him, so when he was supposed to have sexual relations with Tamar he did not complete the sex act. This made it impossible for Tamar to become pregnant and for Er to have descendants.
The Lord will not forgive them. His anger will be like a burning fire against those people, and all the curses written in this book will come on them. The Lord will destroy any memory of them on the earth.
Get away so that I may destroy them and make the whole world forget who they are. Then I will make another nation from you that will be bigger and stronger than they are.”