God chose Abraham to create a nation, Israel. This nation had two purposes. First, Israel was the physical, familial context for Jesus. The Promised One, as God become man, needed a physical, family to become part of. A small, ordinary family in Israel became that family. The writers of the Bible gave the Promised One an “address” so people would know where to find him.
Second, Israel was God’s representatives to the world. Since the Fall, God has worked to demonstrate his nature, his character, and his plan for people through a group of people who would belong to him. Other people would look at his family, see not only an excellent group of people, but see who God was, and what it meant to live with/for him.
Israel only succeeded as a negative example. They said they would follow the Lord, but only succeeded temporarily. Individuals, who chose from their hearts, worked out better.
A person could always choose to become a part of God’s family. Israel ony understood it from their perspective. They never quite made room for the rest of the world.
But Jesus went out of his way to bring the world into his family. Both Jews and Gentiles make up his family, receive his covenant, and his promises. Gentiles have the same access, the same promises, and the same identity as Jews, who follow him. They are God’s family, God’s people, because they are united to Jesus. There is no longer Jew and Gentile. There is only God’s family.
He broke down what separated the two groups. He ended the system of the Law. He made peace with God’s people. He formed one family from all peoples.
He gave to all who came to him, to follow him, the Holy spirit to live with them. Unity with Christ is the only requirement to peace with God, and unity with God’s family.