Genesis 19
32 Ref Come, let's make our father drink wine, and we will lie with him, that we may preserve our father's seed."
33 Ref They made their father drink wine that night: and the firstborn went in, and lay with her father. He didn't know when she lay down, nor when she arose.
34 Ref It came to pass on the next day, that the firstborn said to the younger, "Behold, I lay last night with my father. Let us make him drink wine again, tonight. You go in, and lie with him, that we may preserve our father's seed."
35 Ref They made their father drink wine that night also. The younger arose, and lay with him. He didn't know when she lay down, nor when she arose.
36 Ref Thus both of Lot's daughters were with child by their father.