Ever since I came into the Reformed Presbyterian church twenty years ago, I've been hearing about this kingdom. Though I grew up in reformed churches, the idea of Jesus being the Mediatorial King over the world for the sake of the Father wasn't a significant part of my thinking. But these covenanters, they had this grip on Jesus-as-King and they refused to let it go. And so I was taught the beauty, power and hope of Jesus' kingship. And with that kingship came lots of talk about the kingdom--which makes sense, since Jesus came proclaiming a kingdom and the apostles kept right on preaching that same kingdom.
But my speaking about the kingdom was always (and remains to a degree) a little sloppy. I began at some point to talk about "building" the kingdom, thinking I was doing Jesus a favor by getting on board with His project. The problem is that the Bible never speaks this way.
Consider the words of theologian David Wells:
We can search for the kingdom of God, pray for it, and look for it, for example, but only God can bring it about (Luke 12:31; 23:51; Mt. 6:10, 33). The kingdom is God's to give and to take away. It is ours only to enter and accept (Mt. 21:43; Luke 12:32). We can inherit it, possess it, or refuse to enter it, but it is not ours to build and we can never destroy it (Mt. 25:34; Luke 10:11). We can work for the kingdom, but we can never act upon it. We can preach it, but it is God's to establish (Mt. 10:7; Luke 10:9; 12:32).
(The Courage to Be Protestant, 196)
The upshot of making our kingdom-talk more Biblical is that it keeps us in the right place and keeps our hope secure. We are seekers of the kingdom, even preachers of the kingdom, but we are not builders. Jesus remains both the architect and builder of His kingdom. This kingdom isn't like a chess board, with a wimpy king relying on his many subjects to protect him and do his will. Rather, Jesus' plan is, clearly, a much better plan than including me on the building team. Our hope in the kingdom, both the already-and-the-not-yet aspects of it, is secure because Jesus is King, because the kingdom has already been established by His crucifixion, resurrection and ascension, and because the Spirit has been sent forth to do the work of making God's kingdom come on earth as it is in heaven.
Finally, consider my favorite Q&A from the Larger Catechism and which parts of this we are responsible for and which parts Christ has promised to accomplish.
Q. 191. What do we pray for in the second petition?
A. In the second petition (which is, Thy kingdom come), acknowledging ourselves and all mankind to be by nature under the dominion of sin and Satan, we pray, that the kingdom of sin and Satan may be destroyed, the gospel propagated throughout the world, the Jews called, the fullness of the Gentiles brought in; the church furnished with all gospel officers and ordinances, purged from corruption, countenanced and maintained by the civil magistrate; that the ordinances of Christ may be purely dispensed, and made effectual to the converting of those that are yet in their sins, and the confirming, comforting, and building up of those that are already converted: that Christ would rule in our hearts here, and hasten the time of his second coming, and our reigning with him forever: and that he would be pleased so to exercise the kingdom of his power in all the world, as may best conduce to these ends.