Charles Ellicott Commentary Genesis 19:32

"come, let us make our father drink wine, and we will lie with him, that we may preserve seed of our father." — Genesis 19:32 (ASV)

That we may preserve seed of our father. —This was a very strong feeling in ancient times, and provides the sole excuse for the revolting conduct of these women. The utter degradation of Lot and his family is the most painful part of his story, which so ends in his intense shame.