These phrases refer to the presence and activity of God on earth, here and now. He acts often by means of His people, so these phrases refer also to them.
The ‘Kingdom of Heaven’ correlates roughly therefore to the Jesus followers living in this world. A passage from Matthew illustrates. Jesus says:
Truly, I say to you, among those born of women there has arisen no one greater than John the Baptist. Yet the one who is least in the kingdom of heaven is greater than he.
What is Jesus saying here? John the Baptist is not part of the ‘Kingdom of Heaven’! That seems counterintuitive. John was, after all, a prophet, and Jesus calls him “more than a prophet.”
John the Baptist is a person whom God chose to do important tasks, and John accomplished those tasks. Why then would John not be reckoned as part of the ‘Kingdom of Heaven’?
To clarify: this text does not mean that John was denied access to the afterlife. Jesus is not telling us that John didn’t get into Heaven. Jesus is not asserting that John failed to receive eternal life.
Rather, Jesus is pointing out that John was part of a preliminary operation on God’s part. John was “preparing the way,” as he often used that phrase from Isaiah.
John’s movement, that large crowd of people from the city who visited him in the desert, was preparatory for the ‘Kingdom of God,’ but it was of itself not that kingdom.
Likewise, those who are not being used as God’s instruments on earth are not included in Kingdom of Heaven. Paul writes in his first letter to Corinth:
Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God.
If one spends one’s time murdering and thieving, then one is not spending one’s time being used by God: then one is not reckoned as part of the ‘Kingdom of God.’ This is not to say, however, that one will fail to receive eternal life, or that one will not be pulled into Paradise.
Parallel texts in Luke and Matthew show that ‘Kingdom of God’ and ‘Kingdom of Heaven’ are indeed synonymous and interchangeable. Otherwise identical passages vary only in this one regard.
That the Kingdom of Heaven is a matter of God’s activity in this world, and not of our future presence in the afterlife, is seen in Mark 1:15, where Jesus says that the Kingdom of God “has come near” or “is at hand.”
In John’s Revelation, a vision of a primordial exile of Satan from God’s presence is given. In it, John hears the announcement:
I heard a loud voice in heaven, saying, “Now the salvation and the power and the kingdom of our God and the authority of his Christ have come.”
Revelation is telling the reader that the Kingdom of God and its ancillaries “have come,” i.e., is already a matter of this world and not of the next world.
Both in the Gospels - so many of parables are about the Kingdom - and in the epistles, texts about the Kingdom are about the present and not about the future. The verb forms reflect this: “the kingdom is like …” not “the kingdom will be like …”
To be sure, there is a connection between being a Jesus follower in this world, and spending eternity in Paradise with God. But the two are not identical.
Peter, while indicating this linkage, encourages virtue, not as a key to the afterlife, but rather as the key to making one’s self the most efficient instrument - as the key to placing one’s self at God’s disposal: making one’s self available as an instrument to be used by God:
For if these qualities are yours and are increasing, they keep you from being ineffective or unfruitful in the knowledge of our Lord Jesus Christ. For whoever lacks these qualities is so nearsighted that he is blind, having forgotten that he was cleansed from his former sins. Therefore, brothers, be all the more diligent to confirm your calling and election, for if you practice these qualities you will never fall. For in this way there will be richly provided for you an entrance into the eternal kingdom of our Lord and Savior Jesus Christ.
Note that Peter tells us that virtues ‘confirm’ our status, but they do not create it. Practicing virtues verifies what is already the case - that we will spend eternity with Jesus and in His presence.
Yet, despite the inefficacy of the virtues to work salvation, there is some connection between virtue and salvation: note Peter’s use of the word ‘eternal’ in the text above.
Peter tells us that the virtues have this effect, that instead of merely entering the Kingdom, we will enter ‘richly’ and ‘abundantly.’
Note also that Peter stresses the ‘eternal’ Kingdom. What is begun in this world continues into the next. One can speak of the Kingdom in this world, i.e., what God is doing by means of His people here and now. Most of the citations in the New Testament speak of the Kingdom in this way.
But Peter adds the adjective ‘eternal’ - he lets the reader know that he’s going to reveal a new aspect of the Kingdom - that it has some connection with the afterlife. This ‘eternal’ Kingdom is somehow connected to the Kingdom of God and the Kingdom of Heaven, to God’s activity here and now using His people as instruments.
