Genesis 19:31-34

"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: 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."

This tragic, pitiful episode stands here as awesome proof that Lot and his family had been in Sodom too long. They had indeed been delivered OUT OF Sodom, but Sodom was still IN them to a certain degree.

The wine. Evidently, Lot brought along his liquor when he left the doomed city. That opened the door for the evil that came later.

The daughters' fear. Their notion that not a man on the earth was left was unjustified. They had only recently left the populous city of Zoar; and their allegation that their father only, of all the men on earth, was left had no foundation in fact and appears here more as an excuse for what they wanted to do than as any heroic deed on their part to preserve humanity. Robinson supposed that the daughters might have thought the destruction was universal and wrote that, "In that case, Lot's daughters must be regarded as heroines who adopted desperate measures to repopulate the earth!"[20] Such views are impossible of reconciling with what is written here.