Genesis 19:34-38

34The next day the firstborn said to the younger, “Look, I slept with my father last night. Let’s get him to drink wine again tonight so you can go sleep with him and we can preserve our father’s line.”

35That night they again got their father to drink wine, and the younger went and slept with him; he did not know when she lay down or when she got up.

36So both of Lot’s daughters became pregnant by their father.

37The firstborn gave birth to a son and named him Moab. He is the father of the Moabites of today.

38The younger also gave birth to a son, and she named him Ben-ammi. He is the father of the Ammonites of today.