What does the Bible say about the nature of God's kingdom?

Scripture emphasizes that the kingdom of God is not of this world, as seen in John 18:36 where Jesus states, 'My kingdom is not of this world.' The expectation of a physical kingdom led the disciples to misunderstand Jesus' mission, similar to how many today may cling to external religious forms rather than seeking the true essence of faith. The Old Testament prophecies point to a spiritual reign, where the true blessings and presence of God are experienced in the hearts of believers rather than through earthly establishments.