Genesis 19:31-36

31The firstborn said to the younger, “Our father is aging, and there is not a man on earth [available] to be intimate with us in the customary way [so that we may have children].

32Come, let us make our father drunk with wine, and we will lie with him so that we may preserve our family through our father.”

33So they gave their father wine that night, and the firstborn went in and lay with her father; and he did not know when she lay down or when she got up [because he was completely intoxicated].

34Then the next day, the firstborn said to the younger, “Behold, I lay with my father last night; let us make him drunk with wine tonight also, and then you go in and lie with him, so that we may preserve our family through our father.”

35So they gave their father wine that night also, and the younger got up and lay with him; and again he did not know when she lay down or when she got up.

36Thus both the daughters of Lot conceived by their father.