Genesis 19:37

And the firstborn bare a son, and called his name Moab: the same is the father of the Moabites unto this day.

The firstborn daughter bore a son and called his name Moab, and he is the father and ancestor of the Moabites, a people still known by that name in the time of the verse. The birth took place after leaving Sodom, after Lot left Zoar for the mountains and dwelt in a cave, stripped of all for which he had exposed his family to a wicked city.

The birth came through Lot's grave moral failure and the sinful conduct of his daughters, caused by the wicked associations formed in Sodom. Living among corrupt Sodomites perverted their morals and so interwove corruption with their character that it confused their sense of right and wrong, so that they could not distinguish good and evil and incest did not appear as sin to them. Though Lot with his two daughters was rescued from destruction, they remained corrupted in morals by their sojourn there, and the curse of Sodom followed them even to the mountain cave. Moab's descendants the Moabites, together with the Ammonites as Lot's only posterity, became vile, idolatrous tribes, rebels against God and bitter enemies of His people.

This descent from Lot explains why Israel was commanded not to molest the Moabites as it traveled east of their land. The verse belongs to the account of Sodom, whose destruction is an example of judgment from which only a few escaped after receiving warning. Sodom was consumed for the same crime found among the Canaanites.

The account of Lot's sin is preserved as a truthful record of human failure and of the failures of believers, kept as a warning about sin and disobedience and to instruct later generations, not as an excuse for wrongdoing. The verse stands as a warning to all who wish to live godly lives to separate themselves from all influences calculated to lead them away from God, for remaining long among the wicked blunts spiritual discernment and costs more than any worldly riches gained there. Sodom from the same chapter is an example of a place associated with depraved practices that youth should avoid.