NOTES for Luk 17:20-21
Throughout all three years of His earthly ministry, the Lord Jesus Christ speaks of what is concentrated in compressed form in these words, yet finds understanding in few. Even after the Resurrection and Pentecost, this revelation remains one of the most difficult to understand in all Christianity. For some reason, the fact that the Kingdom of God will not come in an observable way very often disappoints us, and we try not to think about these words. The point may be that these words of the Savior imply that outside us, in the world in which we live, we will see not stirring and beautiful manifestations of the Kingdom of God, but sorrow and suffering. Only in our own heart does the Holy Spirit grant us comfort and the experience of the presence of the Kingdom of God. And this is very hard; to accept it means accepting Christ's word that whoever wants to follow Him must take up the cross.
Yet the Lord did not want to disappoint us when He said this. On the contrary, in these words He reveals to us an amazing hope. The coming of Christ's Kingdom in power and glory is possible only at the end of time, when God's judgment sums up history. But, says the Lord, that very coming Kingdom which the prophets see as the completion and goal of history is already given to us today, not as a promise, but as an accomplished fact. This Kingdom is inside, deep in human hearts, and often it is unnoticeable not only to those around us but even to the person himself; the Lord also warns His disciples about this. But it already exists, we are already its citizens, and it is already manifest in our heart and our life.
The Kingdom of God differs from all earthly states known to us first of all in that all the subjects of this Kingdom obey the King directly. In the Kingdom of God there is no room for what our present language calls the "vertical of power," because that is needed only in an earthly state. This immediacy of each person's relationship with God is the great gift of the Kingdom, sharply distinguishing it both from the Old Covenant and, even more, from everything pagans could have imagined. Precisely because God reveals His Kingdom within people, in their hearts, it already here and now becomes for us the source of life, what Christ calls "a spring of water flowing into eternal life."