Genesis 19:34-38

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. 36And both the daughters of Lot were with child by their father. 37And the first-born bore a son, and called his name Moab: the same is the father of the Moabites to this day. 38And the younger, she also bore a son, and called his name Ben-ammi; the same is the father of the children of Ammon to this day.