"You say that I am a king"
from one of St. Augustine's homilies on the Gospel of John:
Listen, everyone, Jews and Gentiles, circumcised and uncircumcised. Listen, all kings of the earth. I am no hindrance to your rule in this world, for my kingdom is not of this world. Banish the groundless fear that filled Herod the Great on hearing that Christ was born. More cruel in his fear than in his anger, he put many children to death, so that Christ also would die. But my kingdom is not of this world, says Christ. What further reassurance do you seek? Come to the kingdom not of this world. Be not enraged by fear, but come by faith. In a prophecy Christ also said: He, that is, God the Father, has made me king on Zion his holy mountain. But that Zion and that mountain are not of this world.
What in fact is Christ's kingdom? It is simply those who believe in him, those to whom he said: You are not of this world, even as I am not of this world. He willed, nevertheless, that they should be in the world, which is why he prayed to the Father: I ask you not to take them out of the world, but to protect them from the evil one. So here also he did not say: My kingdom is not in this world, but is not of this world. And when he went on to prove this by declaring: If my kingdom were of this world, my servants would have fought to save me from being handed over to the Jews, he concluded by saying not "my kingdom is not here," but my kingdom is not from here.
Indeed, his kingdom is here until the end of time, and until the harvest it will contain weeds. The harvest is the end of the world, when the reapers, who are the angels, will come and gather out of his kingdom all causes of sin; and this could not happen if his kingdom were not here. But even so, it is not from here, for it is in exile in the world. Christ says to his kingdom: You are not of the world, but I have chosen you out of the world. They were indeed of the world when they belonged to the prince of this world, before they became his kingdom. Though created by the true God, everyone born of the corrupt and accursed stock of Adam is of the world. On the other hand, everyone who is reborn in Christ becomes the kingdom which is no longer of the world. For so has God snatched us from the powers of darkness, and brought us into the kingdom of his beloved Son: that kingdom of which he said: My kingdom is not of this world; my kingly power does not come from here.