Now Jesus began His ministry with these words in [Matthew 4:17] NRSV “Repent, for the kingdom of heaven has come near” Then again when Jesus sent forth His twelve disciples to the lost sheep of Israel, He said to them in [Matthew 10:7] NKJV “And as you go, preach, saying ‘The kingdom of heaven is at hand’” He also said to His disciples in [Luke 9:27] NRSV “But truly I tell you, there are some standing here who will not taste death before they see the kingdom of God.”
Surely if the kingdom was at hand during the beginning of Jesus’ ministry then we ought to be seeing it right now, don’t you think? in fact Jesus did mention that there would be some who would see it before they die. Or did Jesus make a mistake? No, in fact the kingdom of God was manifested right from the time of Jesus. How can I say that? Okay let’s take a look. In the 12th chapter of Matthew, Jesus heals a demon-possessed, blind and mute man, [Matthew 12:23] NKJV says ‘And all the multitudes were amazed and said, “Could this be the Son of David?”’ This is where the Pharisees, who were against Jesus simply because their stubborn and religious minds could not accept Him as the Messiah, said that Jesus cast out demons by Beelzebub, the ruler of demons. Jesus began to explain to them that a kingdom divided against itself could never stand and that Satan would not cast out Satan. But look at what Jesus says in verse  “But if I cast out demons by the Spirit of God, surely the kingdom of God has come upon you”**
This is a clear indication that the kingdom of God ‘had already come’ to the people as professed by Jesus. Looking at Jesus’ statement we see that the ‘Spirit of God’ is what the kingdom of God is all about. What is this Spirit of God? It is the Holy Spirit. Wasn’t the Holy Spirit present all the while even when God created the universe [Genesis 1:2], so what is different about the Holy Spirit from the time of Jesus that we should say that the kingdom of God has come to us? God is Spirit [John 4:24] and is manifested to us as one God in three persons, the Father, the Son and the Holy Spirit [Matthew 28:19], but this present and continuing ministry of the Holy Spirit began only with the coming of Jesus, prior to that the Holy Spirit was at work only for specific tasks that God the Father required Him to do.
Jesus Himself was baptized with the Holy Spirit in [Matthew 3:16] and wherever He went, He preached the gospel of the kingdom and healed sicknesses and disease among the people [Matthew 9:35]. The word “gospel” is translated from the Greek word ‘euaggelion’ which means good news. Certainly Jesus was preaching good news which is why crowds were drawn to Him. Now this good news was about the kingdom of God which was not just mere words that Jesus preached but it was with power [1 Corinthians 4:20] of the Holy Spirit that healed the people from their sicknesses and diseases. Plain words alone would not have attracted people, but in fact it was the power of the Holy Spirit and all that He accomplished which drew the multitudes to Jesus. The Holy Spirit was active and at work, though He could not be seen physically.
Therefore to understand the kingdom of God we need to be mindful that there is a spiritual realm in which the Holy Spirit has already manifested Himself in the world today and there will yet be a physical manifestation of the kingdom sometime in the future. The Holy Spirit plays a vital role in this kingdom; after all it is only through the work of Holy Spirit that a person can enter into the kingdom. And to fully function in this kingdom we would have to accept and receive Jesus as our Lord and Savior and be equipped by receiving the Holy Spirit like a child which is what Jesus was talking about [Luke 18:17].