Perhaps you want to ask me what I mean exactly by saying that the judgement-death of Christ set up a real and actual kingdom of holiness. It is a point which it is easier for faith to realise than for theology to explain. But the answer would lie along this line: What Christ presented to God for his complete joy and satisfaction was a perfect racial [that is, the whole human race] obedience. It was not the perfect obedience of a saintly unit of the race. It was a racial holiness. God's holiness found itself again in the humbled holiness of Christ's 'public person.' He presented before God a race he created for holiness. Remember that the very nature of our faith in Christ is union with him. The kingdom is set up by Christians being united with the work, the victory, the obedience, the holiness of the king.
Christ, in his victorious death and risen life, has power to unite the race himself, and to work his complete holiness into its actual experience and history. He has power, by uniting us with him in his Spirit, to reduce time to acknowledge in act and fact his conclusive victory of eternity. When you think of what he did for the race and its history, you must on no account do what the church and its theology has too often done - you must not omit our living union with him. It is not enough to believe that he gained a victory at a historic point. Christ is the condensation of history. You must go on to think of his summary reconciliation as being worked out to cover the whole of history and enter each soul by the spirit. You must think of the Cross as setting up a new covenant and a new humanity, in which Christ dwells as the new righteousness of God. 'Christ for us' is only intelligible as 'Christ in us' and we in him. By uniting us to himself and his resurrection in his spirit he becomes the eternal guarantee of the historical consummation of all things some great day.
From pages 118-9 of P T Forsyth's The Work of Christ