Through which nation did the Messiah come?
The Messiah came through the nation of Israel. Israel was the vehicle God used all along, as the lineage and promises were Jewish, not Gentile. The context emphasizes that Gentiles are excluded from this lineage; the fulfillment was Jewish.
Les explains that the Messiah came through Israel, and Israel was to be the vehicle all the way along. He notes that the subject in verse 25 excludes Gentiles because Gentiles aren't in the lineage of Israel—they cannot be pushed into the Israeli nation. This is Jewish. Les also points back to Isaiah chapter 42 to show this truth from the Old Testament.