In this verse, Jesus introduces a second facet of the Kingdom of God, teaching that a person can enter into it, as well as that one must be "born again" to bring about the entrance. The question arises, "How long must one wait before entering it?"
Jesus preached the gospel of the Kingdom of God (Mark 1:14-15), as did Paul (Acts 28:30-31). The Bible states plainly that the Kingdom is an entity that one can enter into even before Jesus' return. Note Matthew 5:20, "For I say to you, that unless your righteousness exceeds the righteousness of the scribes and Pharisees, you will by no means enter the kingdom of heaven." Jesus adds in Matthew 7:21, "Not everyone who says to Me, 'Lord, Lord.' shall enter the kingdom of heaven, but he who does the will of My Father in heaven.'" Moreover, Jesus declares in Matthew 18:3, "Assuredly, I say to you, unless you are converted and become as little children, you will by no means enter the kingdom of heaven." Clearly, a person can enter into God's Kingdom, but there are also requirements. Can one meet the requirements now?
In Mark 1:15, Jesus dogmatically states, "The time is fulfilled, and the kingdom of God is at hand." "The time is fulfilled" implies that nothing can be added to it, that time will be extended no longer. That the Kingdom is "at hand" means that it is near or close. It does not suggest distance in either space or time. By using these phrases together, Jesus indicates that it can be entered into at once when God's basic requirements are met. The most basic requirement is taught in John 3—to be born again. Jesus thus announces when the Kingdom could be entered—immediately.
Luke 17:20-21 finds Jesus speaking to a group of Pharisees:
Now when He was asked by the Pharisees when the kingdom of God would come, He answered them and said, "The kingdom of God does not come with observation; nor will they say, 'See here!' or 'See there!' For indeed, the kingdom of God is within you."
It is evident that the Pharisees' conception of the Kingdom of God differs from that of Jesus. They believed in a spectacular, visible establishment of the Kingdom, even as we look forward to its fulfillment in the near future. However, in Luke 10:9, 11 and again in Luke 11:20, Jesus plainly says that it was already present, whether in the persons of the apostles or Himself, as exhibited in their acts. Acts can include miracles, conduct, and their messages. His statement in Luke 17:20-21 explains that they should not expect a visible manifestation of the Kingdom as they perceived it at that time.
Theologians may argue over the interpretation of words, but Jesus' own testimony undoubtedly implies that the Kingdom of God was in their presence in His Person and ministry. Therefore, the last phrase of Luke 17:21 should be translated as, "The kingdom of God is among you." Barnes' Notes, Tyndale New Testament Commentary, Expositor's Bible Commentary, The New International Biblical Commentary, and The Interpreter's Bible all agree on this conclusion. He was in their midst, and He was within the Kingdom of God.
When this is combined with John 18:36 (where Jesus declares that His Kingdom "is not from here") and many other scriptures pointing to the establishment of God's Kingdom with power at Christ's return, we can understand that it is both a present and a future reality. In addition, it has both heavenly and earthly aspects. On one hand, it is present and near in the people to whom God has given His Spirit and has chosen to represent Him. On the other, it is distant in terms of time and as a geographical and governing reality. As a present reality, it is small, goes virtually unnoticed, and rules over little. Yet, in the future, at Christ's return, it will dominate and rule the earth. It is certainly not established in its fullness on earth now. Nonetheless, Scripture also proves that it is a present, earthy reality having earth-bound, flesh-and-blood citizens who are, in the Bible's terms, "spiritually minded" or "in the Spirit."
We are all familiar with Matthew 13, in which almost every parable begins, "The kingdom of heaven is like" (verses 24, 31, 33, 44, 45, 47, 52). Jesus then illustrates a matter that directly involves instruction for the church and its membership. In doing this, He is using the term "kingdom of heaven" in place of "the church"—He is virtually equating them. Why? Because church members are citizens of the Kingdom of God.
Notice especially verse 41. How can angels gather tares, not just from any old place, but from out of Jesus' Kingdom on earth, if it does not yet exist on earth? Christians are not only presently God's children in the Kingdom, but tares fellowship with them in the church! Again, in Mark 12:28-34, Jesus converses with a scribe whom He had complimented after seeing the man respond wisely, saying, "You are not far from the kingdom of God." He means that the scribe is not far from being converted and entering the Family of God.
When Jesus and the apostles preached the gospel, they were inviting people to become part of that Kingdom immediately without having to wait for the resurrection at Christ's return. The Kingdom of God is a spiritual entity. Its headquarters is in heaven, but at the same time its agents—initially Jesus of Nazareth then later the apostles and the church—were, as children of God, laboring on earth to make it better known and expand its citizenry.
The Kingdom of God is that entity in which those who are part of it recognize and submit to the rule of the Father and Son. A person becomes part of it by being born again, and those who are born again become sons of God. God's Kingdom as presently configured consists of God the Father, His Son Jesus Christ, and all the children of God who have entered the Family of God by means of God's calling, being born again, and receiving God's Holy Spirit.
John W. Ritenbaugh
Born Again or Begotten? (Part One)