Genesis 19
31 Ref And the first-born said unto the younger, Our father is old, and there is not a man in the earth to come in unto us after the manner of all the earth:
32 Ref come, let us make our father drink wine, and we will lie with him, that we may preserve seed of our father.
33 Ref 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.
34 Ref 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.
35 Ref 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.
36 Ref Thus were both the daughters of Lot with child by their father.