Ruth as representative redeemer

The intro to Ruth in The Books of the Bible notes that Genesis to Judges traces the formation of the nation of Israel, and Samuel–Kings details the development of the monarchy. In between is Ruth, which begins "In the days when the judges ruled" and ends with the genealogy of King David. Ruth is a bridge book that tells the story of how Israel's beloved (most of the time, anyway) king could be a fourth-generation Moabite.

Remember in the preceding narrative that the Moabites made life difficult for their second cousins the Israelites as the latter fled from centuries of slavery. The curse for this inconsiderate treatment was that no Moabite would enter YHWH's assembly even to the tenth generation. Part of me says this meant NEVER, but some people took it literally. So if you had Moabite blood, you had to prove that it was at least ten generations ago before you could worship in the temple.

How could David get way with entering YHWH's presence, let alone become the leader of YHWH's people, after only four generations? His great-grandmother Ruth redeemed the Moabites. Sure, the story points out that it's Elimelek's family name that's redeemed, and by extension Ruth herself, but note what happens. In the bigger picture, a Moabite could now point to King David and say, "He gets into the assembly. Why not me?" And it was Ruth's kindness and commitment to follow Naomi and YHWH that brings about this change.

Two women in a desperate situation somehow change the course of foreign relations because the foreigner behaved like a true Israelite. This is where trickle-up foreign relations works. Ruth removed the curse of her entire people by doing exactly what her ancestors failed to do the first time.