From On Prayer, 25 (ca. 233)
According to the words of our Lord and Savior, the kingdom of God does not come in such a way for all to see. No one will say: “Behold, here it is!” or “Behold, there it is!” because the kingdom of God is within us. Indeed, the Word of God is very near, in our mouth, and in our heart. Thus it is clear that one who prays for the coming of God’s kingdom prays rightly to have it within, that there it may grow and flourish and reach its full potential. For God reigns in each of his holy ones. Anyone who is holy obeys the spiritual laws of God, and God dwells within that person as within a well-governed city. The Father is present within him, and Christ reigns with the Father in the mature soul, as it says in Scripture, “We shall come to him and make our home with him.”
Thus the kingdom of God is within us, as we continue to make progress, will reach its full potential when the apostle’s words are fulfilled, and Christ, having subjected all his enemies to himself, will hand over his “kingdom to God the Father, that God may be all in all.” Therefore, let us pray unceasingly with that disposition of the soul which the word may make divine, saying to our Father who is in heaven, “Hallowed be your name, your kingdom come.”
Note this too about the kingdom of God. There is no partnership between justice and iniquity, no compromise between light and darkness, no commerce between Christ and Belial. The kingdom of God cannot coexist with the reign of sin.
Therefore, if we wish God to reign in us, in no way “should sin reign in our mortal body.” Rather we should put to death what is base in us and bear fruit in the Spirit. There should be in us a kind of spiritual paradise where God may walk and be our sole ruler with his Christ. In us the Lord will sit at the right hand of that spiritual power which we wish to receive. And he will sit there until all the enemies which rage within us become his footstool, and every principality, authority, and power within us is cast out.
All this can happen in each one of us, and the last enemy, death, can be destroyed; then Christ will say in us: “O death, where is your sting? O hell, where is your victory?” Now therefore, let what is perishable in us clothe itself in holiness and imperishability. Let what is mortal be clothed, now that death has been conquered, so that God will reign in us, and we shall enjoy even now the blessings of rebirth and resurrection.
Origen (ca. 185-254) was an Egyptian scholar and theologian, who taught at the Catechetical Schools of Alexandria and Caesarea wrote extensive Biblical commentaries and theological treatises. He was the greatest of the Alexandrian theologians and his allegorical methods of interpretation deeply shaped subsequent Biblical study and ascetical practice. His treatise On Prayer is the earliest extant commentary on the Lord’s Prayer.