It would then have to be proved explicitly and in detail that Jesus only appeared in Israel because that was his place of origin, because he was naturally shaped in some way, like every human being, by the history of his people, but that otherwise he had set himself apart from Israel's history of election. And yet there is not the faintest evidence of such a thing. It simply cannot be produced. Precisely where Jesus (like John the Baptizer before him) calls into question the participation of Israel, or part of Israel, in ultimate and definitive salvation (cf. Matt 8:11-12) he presumes Israel's salvation-historical function. But above all there is an overabundance of texts to show that Jesus did not abandon the fundamental constant we have described. I will speak of those texts at length in the following chapters. Most important of these is the choice of the Twelve--a demonstrative sign-action showing that Jesus cared about the twelve tribes of Israel. The Twelve are a visible sign and, of course, also an "instrument" of his will to gather all Israel. And why? For the sake of Israel? No, for the sake of the world!
The principle behind this is pointedly formulated in James's speech in Acts 15, aided by a mixed quotation based on Amos 9:11-12:
After this I [the Lord] will return, and I will rebuild the tent of David, which has fallen; from its ruins I will rebuild it, and I will set it [the tent] up, so that all other peoples may seek the Lord--even all the Gentiles over whom my name has been called. Thus says the Lord, who has been making these things known from long go. (Acts 15:16-18)The sense of this combined quotation is that the fallen Israel must be rebuilt precisely in order that the Gentile nations, over whom the name of the Lord has been called out, may seek and find God. They cannot perceive him otherwise. The ultimate goal of the rebuilding of Israel is the coming of the Gentiles. Jesus thought no differently.
Obviously this resolute will of Jesus to gather all Israel (for the sake of the nations) had everything to do with his proclamation of the reign of God. The two are inseparable...
Jesus of Nazareth by Gerhard Lohfink