Genesis 19:33-38

That night, they got their father drunk with wine, and the firstborn went in and slept with him. Lot was so drunk he didn’t have a clue about what had happened. The next day, the firstborn said to the younger, “I slept with my father last night. Tonight, it’s your turn. We’ll get him drunk with wine, and you can sleep with him and we can preserve our family line through our father.” So they got their father drunk the second time; and the younger went in and slept with him. He was once again so drunk he had no clue what had happened. As a result, both Lot’s daughters became pregnant by their father. The older daughter had a son named Moab, who is the ancestor of the Moabites of today. The younger also had a son named Ben-Ammi, the ancestor of the Ammonites of today.