30 Then Lot went up out of Zoar and dwelt in the mountains, and his two daughters were with him; for he was afraid to dwell in Zoar. And he and his two daughters dwelt in a cave.
31 Now the firstborn said to the younger, “Our father is old, and there is no man on the earth to come in to us as is the custom of all the earth.
32 Come, let us make our father drink wine, and we will lie with him, that we may preserve the lineage of our father.”
33 So they made their father drink wine that night. And the firstborn went in and lay with her father, and he did not know when she lay down or when she arose.
34 It happened on the next day that the firstborn said to the younger, “Indeed I lay with my father last night; let us make him drink wine tonight also, and you go in and lie with him, that we may preserve the lineage of our father.”
35 Then they made their father drink wine that night also. And the younger arose and lay with him, and he did not know when she lay down or when she arose.
36 Thus both the daughters of Lot were with child by their father.
37 The firstborn bore a son and called his name Moab; he is the father of the Moabites to this day.
38 And the younger, she also bore a son and called his name Ben-Ammi; he is the father of the people of Ammon to this day.
The angels had told Lot to go out of Sodom up into the mountains (Genesis 19:17), but Lot had negotiated and been allowed to go to Zoar instead. Apparently he didn’t stay there long, but we aren’t told why. He and his two daughters had gone from the luxury of Sodom to the poverty of a cave.
[Lot’s] daughters, on successive nights, encourage him to drink himself into a stupor and then to have sexual intercourse with them. In partial defense of their actions, we may note that they were not motivated simply by physical lust, although certainly their surroundings in Sodom had been most conductive to its full expression. They were, nevertheless, still virgins (Genesis 19:8), so at least their father’s moral standards had influenced them to some degree. They had kept themselves pure for their future husbands, but now it suddenly seemed that they would never have husbands at all. The worst of it was that, now that their brothers, their sisters, and their mother had perished, neither they nor their father would leave any descendants. In view of both God’s primeval command to be fruitful and the universal belief that barrenness therefore was a disgrace, situation seemed intolerable to them. It perhaps was further aggravated by their fear that, with neither husbands nor sons, there would be no one to provide for them as they grew older. Unaccustomed to walking by faith in God to meet their needs, they reasoned that the only possible way out of the intolerable situation was that of incest with their father.
They knew that their father would no willingly consent to such a thing, however. As far as their own moral scruples were concerned, they perhaps reasoned that this would not be as bad as the proposal that their father had made concerning them to the Sodomites. Also, as noted before, there were as yet no actual Scriptural ordinances against incest, and close marriages were not uncommon (e.g., Abram and his half-sister Sarai); so this could not have seemed as serious a crime to them as it would to us today. Evidently they decided it was the only thing to do under the circumstances (except to trust God, and idea which apparently never occurred to them at all), and so proceeded to get their father drunk and to go through with it. — Morris, page 358.
The son of the older daughter was named Moab (meaning “from the father”), and was the progenitor of the Moabites. The younger daughter’s son was named Benammi (meaning “son of my people”), and from him were descended the Ammonites. The Moabites and the Ammonites were frequently at war with Israel in later years. They lived mostly in the mountainous regions east of the Dead Sea. Although they were generally idolaters, not all of them were evil. Ruth, for example, was a Moabite woman and, as the wife of Boaz, became one of the ancestors of Jesus. Naamah, an Ammonite woman, was one of Solomon’s wives and the mother of King Rehoboam, who also was in the ancestral line leading to Jesus. Although God in later years judged the Moabites and Ammonites severely, there is some indication that they may be revived in the last days (Jeremiah 48:47; 49:6). These people, along with the Edomites and others, have today long since been essentially amalgamated with the Arabs, descendants of Ishmael. Whether they will ever again be identified as distinct nations or (as seems more likely) will simply share in the future destiny of the Arabic peoples, only the future will reveal. — Morris, pages 358-359.