Read Genesis 19:34 Using Other Translations
And it came to pass on the morrow, that the firstborn 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.
The next day, the firstborn said to the younger, "Behold, I lay last night with my father. Let us make him drink wine tonight also. Then you go in and lie with him, that we may preserve offspring from our father."
The next morning the older daughter said to her younger sister, “I had sex with our father last night. Let’s get him drunk with wine again tonight, and you go in and have sex with him. That way we will preserve our family line through our father.”