Genesis 19:31-35

Then the firstborn said to the younger, “Our father is old, and there is not a man on earth to have relations with us according to the custom of all the earth.

Come, let’s make our father drink wine, and let’s sleep with him so that we may keep our family alive through our father.”

So they made their father drink wine that night, and the firstborn went in and slept with her father; and he did not know when she lay down or got up.

On the following day, the firstborn said to the younger, “Look, I slept last night with my father; let’s make him drink wine tonight too, then you go in and sleep with him, so that we may keep our family alive through our father.”

So they had their father drink wine that night too, and the younger got up and slept with him; and he did not know when she lay down or got up.