“The image of God’s people as exiles among the nations…originated in Old Testament Israel’s experience of deportation and exile. Luke’s account [in Acts] of the movement of the gospel from Jerusalem outward depicts a literal diaspora of the Jerusalem church, driven by persecution from Jerusalem, some as far as Antioch, where the Gentile mission first began in earnest. With the loss of a sense of a physical center of the Christian movement in Jerusalem, the way is clear for writers like the authors of Hebrews and 1 Peter to represent Christians anywhere as aliens and exiles among the nations, sojourning like the patriarchs in lands that are not their own, awaiting their homecoming to the heavenly Jerusalem that will come down to earth in the future. In modern times this image has sometimes suffered from association with a non-biblical kind of otherworldliness, but its positive significance for mission is its call to the church to be a counter-cultural movement, living for a different God in a different way and with a different future in view.
It may be that this image will come into its own again as the church in the postmodern west reconceptualizes its missionary relationship to a post-Christian society. The church in the west may have to get used to the idea that its own center in God, from which it goes out to others in proclamation and compassion, is actually a position of social and cultural exile or marginality. This may improve its witness to the Christ who was himself so often found at the margins.” (Richard Bauckham, Bible and Mission: Christian Witness in a Postmodern World, pp. 80-81)