Polycarp was a very early Christian author and leader who wrote a letter to the Philippians between the years a.d. 110 and 140. According to Irenaeus who had heard Polycarp speak once in his youth, Polycarp had been a follower of the Apostle John. As an old man, the government arrested and executed Polycarp on the charge of professing Christianity. Here is what Polycarp says about the kingdom. Unsurprisingly, it sounds very similar to what we find in the New Testament:
To the Philippians 5.2-3
2 Similarly, deacons must be blameless in the presence of his righteousness, as servants of God and Christ and not of people. They must not be slanderers, not insincere, not lovers of money, but self-controlled in every respect, compassionate, diligent, acting in accordance with the truth of the Lord, who became a servant of all. If we please him in this present world, we will receive the world to come as well, inasmuch as he promised that he will raise us from the dead and that if we prove to be citizens worthy of him, we will also reign with him–if, that is, we continue to believe. 3 Similarly, the younger men must be blameless in all things; they should be concerned about purity above all, reining themselves away from all evil. For it is good to be cut off from the sinful desires in the world, because every sinful desire wages war against the spirit, and neither fornicators nor men who have sex with men (whether as the passive or as the active partner) will inherit the kingdom of God, nor will those who do perverse things.
To the Philippians 11.2
But how can someone who is unable to exercise self-control in these matters preach self-control to anyone else? Anyone who does not avoid love of money will be polluted by idolatry and will be judged as one of the Gentiles, who are ignorant of the Lord’s judgment. Or do we not know that the saints will judge the world, as Paul teaches?
[Polycarp, The Letter of Polycarp to the Philippians, trans. Michael Holmes, 2007]
In Polycarp’s mind, how we live plays a great role in determining where we will end up. In other words, he does not separate our hope from our lifestyle. Because of our destiny to inherit the kingdom, we should live righteously in the present. Our aim is to please the Lord in this age so that we will receive the future age when resurrection happens.
Notice how Polycarp thinks temporally rather than spatially. He does not talk about going “up” to heaven or “down” to hell at death. Rather he looks “forward” to when the future kingdom arrives. He looks forwards not upwards. The question is not “Where will I spend eternity?” but “Will I enjoy the future age?” He understands, as Paul teaches, that those who turn away from sinful lives in the present will judge the world in the future.