Matthew Poole and continuators on Genesis 19:32

32 Come, let us make our father drink wine , and we will lie with him, that we may preserve seed of our father .

Which they carried with them amongst other necessary provisions either from Sodom or Zoar.

Which though an incestuous and abominable action, yet they thought was made lawful by the supposed necessity, as in the beginning of the World the Marriage of Brethren and Sisters was lawful, because necessary, and when it ceased to be necessary, because of the increase of mankind, it became incestuous.