There is no question that Jesus was born a Jew but did he live as a Jew? Jesus came to fulfil the Law so he had to be the perfect Jew, better than the Pharisees or any Jew before him. The question we then need to ask is, did he dispense with his Jewishness once he had completed his ministry and, in a sense, he did because he broke down the dividing wall between Jew and Gentile. Paul says, in Christ there is neither Jew nor Gentile. The important thing is that He made peace between the two.
Crucially, Paul says that the Jews own the legacy and only when they are brought into the fold will the Gentiles have the full measure of the truth. Rediscovering the Jewish Jesus clearly gives us a fuller picture of who the historical Jesus was and what he meant by what he taught.
It seems to me that Paul translated the Gospel into 'Christian' beautifully as did the other letter writers but Jesus, in the Gospels, was speaking to Jews as a rabbi, not to Christians as a pastor.
Much of Christian theology that we consider orthodox is modern and taught in the light of Christian tradition. Not only do we need to read the Gospels in the light of the Old Testament but also with reference to the post-exilic culture into which Jesus was born and in which he was taught, lived and breathed.
So is Jesus a Jew? The word 'Jew' means, 'from the land of Judea', so historically Jesus is a Jew, born of the tribe of Judah. He is also the Christ, the Jew's Messiah. But we are told that Jesus is the author of creation and, in him, everything is held together. The Jews are sons of Jacob and while Jesus was, as a man, descended from Jacob he is also the second Adam, the new man of which every tribe and nation is descended, including Jacob.
When the signatory of a covenant dies the covenant dies with him. Jesus as a perfect Jew fulfilled the covenant established by Moses and upon Jesus' death the covenant was nullified. By his blood he established a new covenant, not dispensing with the old but superseding it. All the requirements of the Law were met in Jesus so that none of them are now binding upon us. A new covenant has been established and our only commitment is to renounce the covenant of sin and death and accept Jesus as our righteousness.
To the Jew Jesus is a Jew, to the Gentile Jesus is a Gentile. But he is not a Christian. We do not worship a Christian God. We are the 'Christ ones' but to understand Jesus fully the emphasis must be on the 'Christ' and not the 'ones'. What we are 'in Christ' is not important but that we are in Christ.
We see Jesus in Creation, in the Bible, in Christian tradition, in Jewish tradition, in each other, in humanity, through experience. God reveals himself in so many ways and the temptation is always to worship the god of revelation. But however we see Jesus, that's not what he is. We believe that God has given us his Holy Spirit through whom we can connect with a God who is beyond all understanding. Its only in his Spirit that we can truly know God and because our puny minds cannot contain that knowledge we have to admit our cognitive ignorance.
Its with this tension that we live as fools for Christ. We understand who Jesus is in part and with that working knowledge we seek to do his will and know him better. Its not in our temporal understanding of truth that we worship God in spirit but by his Spirit we can worship him in truth.