The “Kingdom of God” is a divine enterprise of God. One might think of it as God’s government for His people. The complete term does not appear in the Old Testament although the realm is spoken of by God’s prophets often in elevated language, as a realm that one should desire above all things. Generally they describe the grand blessings that are attached to this realm that will materialize in the future effecting all forms of life, including creation itself.
This future state that God was illuminating through the prophets would eventually be understood as the Kingdom of God. Generally, God kept His future enterprise hidden until Christ’ was brought to earth, where He would properly reveal and explain God’s prized activity.
When the era of the New Testament opens, we find Jesus beginning His ministry by announcing that the Kingdom of God was at hand, meaning available to participate in now. (The term Kingdom of Heaven is used in Matthew’s gospel-the two terms are synonymous). It would not be the fullness or breadth that the prophets saw and spoke of, but nevertheless was available in part at this time, and well worth the effort to understand and qualify to enter where possible.
The “Kingdom” became the central topic of Jesus’ ministry. He would talk, teach, preach and demonstrate the blessings available in God’s Kingdom, even the healing power that was available in this unique realm. In Acts 1:3 the text illustrates that even after Jesus was resurrected He would continue teaching about the Kingdom of God until he was taken up and joined with the Father. To restate, in addition to using a wide selection of teaching styles to illuminate the blessings of being in the Kingdom, He would also demonstrate the blessings through His healing and deliverance ministry.
To stress the importance of being in the Kingdom, when Jesus was teaching people not to worry about what they need in this life (for there was sickness and shortages everywhere). He taught the people to simply “seek first the Kingdom of God and His righteousness” and those things that one needs in life will be provided by God. In other words if people get their priorities right, God will supply all they need for a healthy, blessed life.