Parsha Vayeira - Chapter 19 – Verses 30 - 33
Lot and his daughters flee the destruction of Sodom and Gomorrah. The angels told him that the city Zoar would not be destroyed & they should go there, but afraid of staying in Zoar, they went into the hills outside, where they took refuge in a cave. The daughters believe that the whole world has been destroyed & therefore they assumed it was their responsibility to bear children and enable the continuation of the human race. They set into a plan which was abhorrent and immoral but seemed to them to be the only possible action to take. They decided to get their father drunk with wine and slept with him.