Isaiah 11:10 "In that day the Root of Jesse will stand as a banner for the peoples; the nations will rally to him, and his place of rest will be glorious."
Paul quotes this passage in Romans 15:12 with a slight variation: "The Root of Jesse will spring up, one who will arise to rule over the nations; the Gentiles will hope in him."
You might ask, "why did Paul put "Gentiles" in his quote when it isn't in Isaiah?" It was in Isaiah. It just lies behind the word "nations." In the Hebrew Bible, the word nations often refers to those outside of the covenant promise; i.e. Gentiles. Paul was using the prophecy to explain that God's plan included all people; Jew and Gentile.
The question of the Post-Christ New Testament is: "Will Christianity be thrown open to everyone or did Jesus come only to save Jews?"
It's not a question to us today because we have over 1900 years of tradition and we are very comfortable with Jesus, God, the Bible, Sunday worship, and communion.
But have you ever really wondered what we are doing reading Jewish scriptures? The Old Testament wasn't written to us or for us. In fact, it's not a testament at all. It is a covenant. No one died for it, therefore it is not a testament. And why are we claiming our salvation in a Jewish Messiah; or why do we care about the 10 commandments; or why do we believe in the idea of one God over all other gods?These are not ideas that Gentiles came to on their own. There were some righteous Gentiles in the Bible like the Synagogue building centurion of Capernaum in Luke 7 or Cornelius in Acts 10. However these men were influenced by the Jews around them. They acknowledged the God of the Hebrews but they were on the fringes of Judaism. The very best they could hope for was to be a proselyte; a Gentile convert to the Jewish world.
God chose to put His righteousness on display through Abraham's physical descendants. The Law of Moses was given as a condition of this special covenant relationship with Yahweh God. To the Gentile, this special relationship was not possible. To be called a child of God was not an option.
At least until God fulfilled His promise of Genesis 12.
Much of Paul's writing centers on God's master plan of making that "one new man" through the cross of Jesus Christ. It revealed the Master's plan of reconciling the entire world, all nations, to Himself.
To Ephesus he wrote: "But now in Christ Jesus you who once were far away have been brought near through the blood of Christ. For he himself is our peace, who has made the two one and has destroyed the barrier, the dividing wall of hostility, by abolishing in his flesh the law with its commandments and regulations. His purpose was to create in himself one new man out of the two, thus making peace, and in this one body to reconcile both of them to God through the cross, by which he put to death their hostility." 2:13-15
To Galatia he wrote: "He redeemed us in order that the blessings given to Abraham might come to the Gentiles through Christ Jesus, so that by faith we might receive the promise of the Spirit." 3:14
To Rome he wrote: "If some of the branches have been broken off, and you, though a wild olive shoot, have been grafted in among the others and now share in the nourishing sap from the olive root, do not boast over those branches. If you do, consider this: You do not support the root, but the root supports you." 11:17-18
The promise to Abraham was in part to his physical descendants; but how much more have we been blessed above simple land and family! The Jewish people had a relationship with God since their father Abraham walked in faith. That the Gentiles could share in this was more shocking than we in the 21st century can possibly imagine.
Paul says in Romans 4:16 "Therefore, the promise comes by faith so that it may be by grace and may be guaranteed to all Abraham's offspring - not only to those who are of the law but also to those who are of the faith of Abraham. He is the father of us all." Emphasis is mine.
It amazes me. I can call Abraham my father; not because I am a physical descendant, but by our shared faith in El Shaddai, God Almighty.
Hope you feel as special as I do. I am much more appreciative of my standing in faith now because I know of the "root" that supports me and the One who died to bring me into His family.