Genesis 19:32-36

come, let us make our father drink wine, and we will lie with him, that we may preserve seed of our father. And they made their father drink wine that night: and the first-born went in, and lay with her father; and he knew not when she lay down, nor when she arose. And it came to pass on the morrow, that the first-born said unto the younger, Behold, I lay yesternight with my father: let us make him drink wine this night also; and go thou in, and lie with him, that we may preserve seed of our father. And they made their father drink wine that night also: and the younger arose, and lay with him; and he knew not when she lay down, nor when she arose. Thus were both the daughters of Lot with child by their father.