'How we define the kingdom will have a lot to do with whether we think it is already here and, if so, to what extent. Forgivenness of sins and the new birth are not the only things that God promised through the prophets. As we have seen, it includes a sweeping cosmic renewal, with the kingdoms of the world under the domain of Christ. It is the salvation not just of souls but of bodies, and not just of human beings but of the whole creation. Yet the New Testamnet teaches that this kingdom arrives in two phases. Like its head, the church suffers now in humiliation, under the cross, in order in order to reign in future glory with Christ (Rom.8:17). In this intermission, the kingdom is the gospel and the gospel is the kingdom. Wherever Christ is forgiving and renewing sinners by his Spirit through the ministry of the gosple, the King is present and his kingdom is expanding.
This view focuses most clearly on the character and message of the kingdom that we find in the prophets and the Gospels. In both alternatives accounts of the kingdom mentioned above, the emphasis falls on a gepolitical regime, whether it is in terms of a revived theocracy in Israel (including sacrifices) or an ever-expanding, gobal influence on nations and cultures. Both views identify the kingdom with visible power and glory, overlooking the fact that what we have now is a kingdom of grace that is present wherever the gospel is preached and the sacraments are administered. The preoccupation, in both views, seems to be analogous to the expectation of Jesus's contemporaries (even his disciples) prior to Pentecost.'
Michael Horton, The Gospel Commission, p.65.