I've been out of town since Friday, so I haven't been able to participate in this conversation, so I'm going to try and answer things starting from here (and then anything else perhaps brought up throughout the rest of the thread).
That is good news. Why do Christians have to read
the Old Testament at all - when everything there is
only valid for the Jewish people?
The most basic Christian confession is that Jesus of Nazareth was and is the Christ or Messiah. That confession makes no sense apart from the historic and religious context of the Old Testament. Namely of God's solemn promise to bring redemption to a world broken with injustice, sin, and death. To that end we find the promise of the coming Messiah, whose coming meant and means the restoration of the world. Christians confess Jesus is that Messiah, or in Greek, Christ; hence why we call ourselves Christians.
We see in Jesus the advent all God's promises, the spoke around which the wheel of history itself spins. In the writings of the Old Testament Prophets we often see a grand vision of not only Israel's full redemption, but of all nations. The Prophets speak of a time when all people walk hand-in-hand to God's holy mountain, a time when humanity is free of violence, war, suffering, and all injustice. An era where God reigns as King through His anointed, the Messiah. Jesus, likewise spoke of the kingdom of God, and that this kingdom wasn't only a far off, future-flung reality, but was a reality entering into the world then and there, through
Him.
Jesus is God's Messiah, the royal authority through whom God is renewing, restoring, and redeeming all of creation, drawing all human beings to Himself, Jew and Gentile. In and through Jesus is fulfillment, the coming about, of that ancient and grand vision of the Prophets. The resurrection of Jesus Christ, in ancient Christian teaching, is the 8th Day of Creation; Christians saw in the day Jesus rose from the dead as the day God began anew the work of creation, of bringing renewal, restoring all things.
The narrative of the Christian Church in the New Testament is rather incomprehensible without the foundation of Israel, the Prophets, the entire Old Testament. Likewise, Christians believe the Old Testament only really comes into light when read in light of Jesus Christ. The two work in tandem, it is the two-fold witness to Jesus Christ. Christians call them
testaments, they bear
testimony to Jesus.
Otherwise Christianity wouldn't have spread like
it did. No?
Are the Jewish people then still the chosen
people?
Insofar as the Jews are the children of Jacob to whom God made a covenant promise through Moses. Being "chosen" never meant better or especially "special"; rather it meant that God had established a specific and unique covenant with this nation of people. As such the Jewish people are still Jacob's children, that can't be undone.
But according to Christianity there is a new "chosen-ness", in Christ, which is universal. Because in and through Christ God has called the entire human race to a newness of life found uniquely in Jesus of Nazareth, by His death and resurrection and the renewal of all things in and from Him. Jew or Gentile, that doesn't matter, for all are made new, brought into a new life, a new way of being human and having humanity in the New Man, Jesus the Christ. The Israel of old and the Israel of new are one and the same in Jesus Christ:
"Here there is not Greek and Jew, circumcised and uncircumcised, barbarian, Scythian, slave, free; but Christ
is all, and
in all." -
Colossians 3:11
Christ not only reconciles the disparate nations, tribes, tongues, and people groups, Jews and Gentiles; more than this Jesus Christ draws in, joins together, and unites the fullness of the whole human family into Himself, and under the gracious Fatherhood of God. What was once many and divided, is now one and united. One new human person, Jesus the Christ. To whom the whole of heaven and earth is subject, as He reigns King and Lord eternal.
-CryptoLutheran