However, the concept of kingdom is completely opposite to the concept of religion. A kingdom consists of a king with citizens. Citizenship is essentially a legal entity with rights and privileges protected by a constitutional commitment of the king and his government. Keep in mind, that too many "Christians" are religious people, but citizens of the kingdom are legal people. Legal in the sense that by virtue of a spiritual birth each individual in the kingdom has the right and blessings of citizens of this heavenly kingdom. We must be delivered from our religious mindset and have our thinking re-adjusted so that we can take on a regal mindset.
Now religious people have no rights, but legal people do. God has always desired sons who are citizens of His Kingdom, possessing the legal right to be part of His family. Citizenship is always considered a privilege in all kingdoms and nations and is usually reserved for those born into that nation or kingdom. There are special situations where one can become a citizen through privileges extended by the government authority, but birthright is the guaranteed form of sonship and the resulting rights of citizenship. In Jesus, these previous rights are conferred to everyone who trusts in Him.
John 1:12-13 Yet to all who received Him, to those who believed in His name, He gave the right to become children of God. 13) Children born not of natural descent, not of human decision or a husband's will, but born of God
Philippians 3:20-21 But citizenship is in heaven. And we eagerly await a Savior from there, the Lord Jesus Christ, 21) who, by the power that enables Him to bring everything under His control, will transform our lowely bodies so that they will be like His glorious body.
Now something that you may or may not have known, the term "Christian" was originally a derogatory label given by pagans to followers of Christ, even though believers through the centuries have generally accepted the term (which literally means "little Christ") and bore it with honor. Yet the term Christian occurs only twice in the Scriptures.
Suggested additional reading: Acts 26:28-29 and I Peter 4:16-17