Genesis 19:30-38 New Revised Standard Version (NRSV)
The Shameful Origin of Moab and Ammon
30 Now Lot went up out of Zoar and settled in the hills with his two daughters, for he was afraid to stay in Zoar; so he lived in a cave with his two daughters. 31 And the firstborn said to the younger, “Our father is old, and there is not a man on earth to come in to us after the manner of all the world. 32 Come, let us make our father drink wine, and we will lie with him, so that we may preserve offspring through our father.” 33 So they made their father drink wine that night; and the firstborn went in, and lay with her father; he did not know when she lay down or when she rose. 34 On the next day, the firstborn said to the younger, “Look, I lay last night with my father; let us make him drink wine tonight also; then you go in and lie with him, so that we may preserve offspring through our father.” 35 So they made their father drink wine that night also; and the younger rose, and lay with him; and he did not know when she lay down or when she rose. 36 Thus both the daughters of Lot became pregnant by their father. 37 The firstborn bore a son, and named him Moab; he is the ancestor of the Moabites to this day. 38 The younger also bore a son and named him Ben-ammi; he is the ancestor of the Ammonites to this day.