Genesis 19:34-35

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

35So they got their father to drink wine that night also, and the younger daughter went in and slept with him. Again he was not aware of it when she lay down or when she got up.