I think Judaism has something to do with the house of Judah, and as Christ our Lord was promised to come from the tribe of Judah,therefore Christ is the root, and Judaism the tree and christianity grafted into the tree, as where the Jewish people were the natural branches, but some were broken off because of unbelief but the Lord God is able to graft them in again if they no longer remain in unbelief. We as chrsitians are not suppose to boast over the branches which are natural, When christ said He was sent o the house of Israel, we as christians are adopted into spiritual Israel. when some of the Jewish people rejected Christ Paul was chosen to spread the gospel among the dispersed Jewish people living among the gentiles but gentiles also heard the gospel and believed.