Genesis 19:30-35

30And Lot went up from Zoar, and dwelt in the mountain, and his two daughters with him; for he feared to dwell in Zoar. And he dwelt in a cave, he and his two daughters.

31And the first-born said to the younger, Our father is old, and there is not a man in the land to come in to us after the manner of all the earth:

32come, let us give our father wine to drink, and let us lie with him, that we may preserve seed alive of our father.

33And they gave their father wine to drink that night. And the first-born went in, and lay with her father, and he did not know of her lying down, nor of her rising.

34And it came to pass on the next day that the first-born said to the younger, Lo, I lay last night with my father: let us give him wine to drink to-night also, and go thou in, lie with him, that we may preserve seed alive of our father.

35And they gave their father wine to drink that night also. And the younger arose, and lay with him; and he did not know of her lying down, nor of her rising.