"But when they believed Philip as he preached good news about the kingdom of God and the name of Jesus Christ, they were baptized, both men and women" (Acts 8:12).
STUDIED TOGETHER, THE WORDS KINGDOM AND CHURCH HAVE A GREAT DEAL TO TEACH US. The first emphasizes authority, and so the expression “kingdom of God” has to do with God’s rule or authority as King (1 Timothy 1:17). The second conveys the idea of an assembly of persons “called out” from the world to belong to Him (Matthew 16:18). Perhaps we might say that kingdom focuses more on God and His sovereignty, while church looks more specifically at the people — those who have answered the call to come back to God, be forgiven, and live under His rule.
As far as the citizens of the kingdom are concerned, one cannot be a member of the Lord’s church and not be a citizen in His kingdom. The reverse is also true. To be in the kingdom is to be in the Lord’s church (with some responsibilities to other “called out” ones). This is an important point because of the popularity of the “spiritual but not religious” concept. Many who speak favorably of the “kingdom of God” would quickly say they have no desire for anything that could be called “church.” However, in the New Testament, those who were members of God’s kingdom were the same people as the members of Christ’s church, and vice versa. They weren’t two different groups; they were the same group.
In regard to kingdom and church, there is another confusion we need to avoid. The Scriptures do not teach that we are in the “church age” now but the “kingdom age” will begin when Christ comes back and establishes a government on the earth. The kingdom age is right now, and so is the church age. In fact, the very thing that defines the church is that God has “transferred us to the kingdom of his beloved Son” (Colossians 1:13). That’s what a Christian is: a loyal subject in God’s kingdom, joyfully accepting all that Jesus taught about how God’s rule should govern our lives. Jesus Christ did not fail. He began His kingdom, as He said He would. We can accept the gospel — and the kingdom — right now.
"As saints and faithful brethren in Christ at Colossae were delivered from the power of darkness and 'translated into the kingdom of the Son of His love' (Colossians 1:12-14), so the true people of God today are citizens in Christ’s kingdom and a manifestation that His power is yet very much alive" (Robert F. Turner).