The question which Wright raises with this observation is, Where does the church gain its mandate for mission, if not from the words of Jesus? The answer is found in the gospel; the gospel presents itself as the fulfillment of the Scriptures, or the completion of the story of God. Hence, Wright advocates that the mission of God's people is found, and integrally bound, in the story of Israel. His conclusion regarding the Great Commission is thus, "It was the inevitable outcome of the story as the Scriptures told it - leading up to the Messiah and leading on to mission to the nations" (39).
What has struck me through this conversation (and I'm not entirely certain if this has been explored before, though I've not encountered it myself) is that what Matthew has given us at the conclusion of his narrative is the same perspective with which Luke begins Acts. This is the time of the restoration of Israel. As the disciples gather around Jesus at a post-resurrection meal they ask, "Lord, are you at this time going to restore the kingdom to Israel?" (Acts 1:6).
Jesus responds with two points: 1) "It is not for you to know the times or dates the Father has set by his own authority" and 2) "But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth" (Acts 1:7). This statement in Acts is the same assertion given in Matthew: that the work of the church is to take the gospel, through the work of the Holy Spirit, to the world because of the restoration of Israel.
With everything which we should be able to expect from the "Jewish Gospel" Matthew gives the statement of Jesus, "After having gone . . ." or "As you go . . ." (etc.) make disciples of all nations. This can only be interpreted in light of the restoration of Israel motif which was so expected in Second Temple Judaism, as the fulfillment of Israel's narrative. This is the outworking of Jesus as the climax of Israel's story, now being given the rightful rule of messiahship as the one who holds "all authority in heaven and earth."
Matthew also gives the sense of messianic fulfillment in the Great Commission, as the project for the church is to make disciples who are baptized in the name of the Father, Son and Holy Spirit. The restoration of Israel has indeed happened in and through Jesus, who now replaces Israel with his life, death, resurrection and present ruler of the nations. He is the representative of the chosen people of God who now sits upon the throne, completing the image of Daniel 7, as the one lifted from the earth and established by the Ancient of Days.
That his followers should make disciples rather than proselytes comes from the transfer from an age of the Law to the age of the Messiah, which has now come upon the world. This is the fulfillment of Israel's story, the restoration of the people of God, and the in-breaking of the eschatological expectations of salvation. Matthew offers for us here not simply a statement of 'doing' for the gospel (a simple "Go!" imperative), but a statement of mission and restoration for the people of God which now spills out to bless (cf. Genesis 12; 15) and include (cf. Joel 2:32) all who believe in Jesus as Messiah.