How do we know the spiritual nature of Christ's kingdom is true?

The truth of Christ's spiritual kingdom is affirmed by Scripture and was central to the misunderstanding of His contemporaries. The Jews were expecting a physical and political Messiah, which led to their rejection of Jesus. However, Scriptures like John 17:14 demonstrate that the kingdom is characterized not by physical appearances but by the spiritual transformation of the believer. The Apostle Paul also articulates this in Romans 14:17, emphasizing that the kingdom of God is not about external observance but about internal realities that reflect a heart changed by grace.