The notion of “Israel” as the “servant” of God in Isaiah is shaped like an hourglass. It is first the many - the ethnic nation of Israel. But the nation failed. Yet oneServant grew up out of that dry ground (53:2) to bear the sins of Israel, and to serve God in Israel’s place.
He would have many offspring (53:10), and thus the hourglass again widens. First it was the barren woman (54:1-2). Now there are two more images of this offspring. The foreigner and the eunuch (56:3). A eunuch is someone who cannot procreate, either by accident or by choice. Yet, as with the barren woman, God promises to give him a “monument” within His house that’s far more valuable than sons or daughters (5).
And to the foreigner who “joins” himself to the Lord (evocative of Paul’s language of “union” with Christ), God will bring them to His holy mountain and make them full of joy (6-7). Now the hourglass widens even more, for now we discover God’s plan all along was to make His house a house of prayer for all peoples (7). God always had in mind other offspring, besides those already gathered (8).
This is why Jesus would later expel the moneychangers (Mark 11:15). They occupied the Court of the Gentiles - the place reserved for the nations to come and worship Him. He shepherds Israel instead of the corrupt religious leaders (9-12), that all the nations may experience the blessings of Abraham.