Why were the Moabites taboo to the Jews?
Their ancestry traced back to Lot and his daughter, a relationship that made them taboo. God had mandated that the Jews have nothing to do with the Gentiles, so the Moabites were specifically off-limits; no Jew was to associate with them. This explains why a Moabite woman in the genealogy is remarkable.
Les explains that Ruth came from Moab, and the Moabites were taboo. They began with the ancestral relationship of Lot and his daughter, so the Jew was to have nothing to do with them. He notes that God had mandated the Jews were to have nothing to do with the Gentiles, yet here is a Moabite girl in the genealogy. Les then refers to Romans chapter 5 verse 20, stressing that even though this is the Jewish economy under the Law, it is the same God who has never changed; only His responsibilities placed on the human race change.