Secondly, Matthew himself uses these two expressions interchangeably, such as in Matthew 19:23-24.
Matthew 19:23 "Then Jesus said to His disciples, "Assuredly, I say to you that it is hard for a rich man to enter the kingdom of heaven."
Matthew 19:24 "And again I say to you, it is easier for a camel to go through the eye of a needle than for a rich man to enter the kingdom of God."
The following verses all refer to the same thing.
Matthew 6:33 "Seek first the kingdom of God and His righteousness, and all these things shall be added to you.
Ephesians 5:5 "For this you know, that no fornicator, unclean person, nor covetous man, who is an idolater, has any inheritance in the kingdom of Christ and God."
Matthew 13:19 "When anyone hears the Word of the kingdom, and does not understand it, then the wicked one comes and snatches away what was sown in his heart. This is he who received seed by the wayside.
Mark 1:14-15 Now after John was put in prison, Jesus came to Galilee, preaching the gospel of the kingdom of God, and saying, "The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel."
Matthew 13:41 "The Son of Man will send out His angels, and they will gather out of His kingdom all things that offend, and those who practice lawlessness."
Luke 4:43 "But He said to them, "I must preach the kingdom of God to the other cities also, because for this purpose I have been sent."
Like those above, there are a tremendous number of verses in the Bible that mention the "kingdom of God" but they all center around one of three areas.
(1) Christ's authority, or his rule on the earth.
(2) The blessings and advantages of all kinds that flow from his rule.
(3) The subjects of this kingdom who are the truly saved; the faithful.
With that important step behind us we can now explore the meaning of the "kingdom of God."
Various Interpretations
Despite the expression "kingdom of God" being used in a great many verses, there has been a great deal of debate over the years as to exactly what Jesus meant by it. One reason for this is that neither Jesus nor the Bible writers ever defined exactly what they meant by the expression, "the kingdom of God." They simply assumed that their hearers or readers would understand what that term meant.
1) The Kingdom of God lies in the future
In many passages it is clear that the kingdom of God is future. In the Lord's prayer found in Luke 11:2 we pray "Your kingdom come" so the kingdom of God must lie sometime in the future.
Jesus said in Matthew 7:21-23 "Not everyone who says to me Lord, Lord, will enter the kingdom of God", so this must also refer to a future event, especially when Jesus continues and says, "Many will say to me on that day".
Mark 14:25 has Jesus saying, "Assuredly, I say to you, I will no longer drink of the fruit of the vine until that day when I drink it new in the kingdom of God."
There are a great many other passages that associate the coming of the kingdom of God with the final judgment, which of course is in the future.
Luke 13:28-29 "There will be weeping and gnashing of teeth, when you see Abraham and Isaac and Jacob and all the prophets in the kingdom of God, and yourselves thrust out. They will come from the east and the west, from the north and the south, and sit down in the kingdom of God.
Luke 21:31 "So you also, when you see these things happening, know that the kingdom of God is near."
So therefore it cannot be denied that there are a great number of passages in the Bible that indicate that Jesus taught that the kingdom of God was still in the future.
2) The Kingdom of God lies now, in the present
In other passages, however, it is equally clear that the kingdom of God is already here.
Matthew 6:33 "But seek first the kingdom of God and His righteousness, and all these things shall be added to you."
Mark 9:1 "And He said to them, "Assuredly, I say to you that there are some standing here who will not taste death till they see the kingdom of God present with power."
Luke 11:20 "But if I cast out demons with the finger of God, surely the kingdom of God has come upon you."
Luke 16:16 "The law and the prophets were until John. Since that time the kingdom of God has been preached, and everyone is pressing into it."
Mark 10:15 "Assuredly, I say to you, whoever does not receive the kingdom of God as a little child will by no means enter it."
Acts 14:22 "Strengthening the souls of the disciples, exhorting them to continue in the faith, and saying, we must through many tribulations enter the kingdom of God."
1 Thessalonians 2:12 "That you would walk worthy of God who calls you into His own kingdom and glory."
Romans 14:17 "For the kingdom of God is not eating and drinking, but righteousness and peace and joy in the Holy Spirit."
1 Corinthians 4:20 "For the kingdom of God is not in word but in power."
So how should one deal with this apparently contradictory data? Well, lets first analyze what the word "kingdom" means. Perhaps this will provide the key for understanding what Jesus meant by the "kingdom of God." How is the term "kingdom" to be understood? Should it be understood as denoting a physical place? If this is correct then "kingdom" refers to a territory or piece of real estate, an area of space bounded by borders. But if that is so then it is evident that the kingdom of God has not arrived yet. There has been no geographical or cosmic changes that have placed a kingdom of God here on earth. The planet remains today essentially as it was in the time of Christ. No new heavenly territories exist. No place on this planet can be designated "the kingdom of God." On the other hand, we could look at "kingdom" as referring to the rule or reign of a king? The kingdom of God can be looked at as a realm, a domain, a sphere where the king is ruling over his kingdom and over his subjects.
But, the coming of the Son of Man, the sinless shed blood of the Son of God, the resurrection of Jesus Christ, faith turning to sight, believers searching for truth, our victory over sin, the God given gift of the Holy Spirit, the discipleship of the faithful, instructions for us to bear our crosses, and so many other Godly things all have and are taking place and all appear to fall within the kingdom of God.
The plain and simple truth is that the human mind is incapable of understanding the kingdom of God. So I believe that the kingdom of God is both now and not yet. Thus the kingdom of God is "realized" and present in one sense, and yet "consistent" and future in another. This is not a contradiction, but simply the nature of the incredible kingdom of God. The kingdom has come in fulfillment of the Old Testament promises, but at the same time a new covenant has been established. But this new covenant's final manifestation and consummation still lies in the future.
So what is the kingdom of God? It is here right now with God in charge. A believer who has surrendered to God can see it but unbelievers have no idea at all that it exists. Luke 17:20-21 "Now when He was asked by the Pharisees when the kingdom of God would come, Jesus 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."
The kingdom of God also lies in the future. It will be that period of time when all will be true believers, and all will love and follow Our Heavenly Father. The Christ haters and Christ rejecters will all be gone. That is when the true brilliance and glory of the Kingdom of God will shine like a billion suns.
The enjoyment of the firstfruits of the kingdom must be tempered by the fact that we still live by faith and not sight. We still long for the perishable to become clothed with the imperishable, the mortal with immortality. In the meantime we are called to endure to the end. Until then, we are to be good and faithful servants of God and enjoy that part of the Kingdom of God, which we as believers have access to now.