Most of the time when we read about the kingdom in the New Testament it is talking about the church. In Matthew 16:17-19, Jesus proclaims that He will build His church and give Peter the keys to the kingdom. These verses make it clear that when Jesus is talking about the church, He means the kingdom also. Another set of scriptures that are good to remember are Mark 9:1, Acts 1:8, and Acts 2:1-4. In Mark 9:1 Jesus says, “Truly, I say to you, there are some standing here who will not taste death until they see the kingdom of God after it has come with power.” This verse says the kingdom will come with power. In Acts 1:8, Jesus says, “But you will receive power when the Holy Spirit has come upon you, and you will be my witnesses in Jerusalem and in all Judea and Samaria, and to the end of the earth.” This verse says the power will come with the Holy Spirit. In Acts 2:1-4, the Holy Spirit came, so we conclude that the power came and the kingdom came as well, but what came in Acts 2? The church did. So usually when we read about the kingdom in the New Testament, it has reference to the church and vice versa.
However, there are a couple of passages where the term kingdom doesn’t refer to the church, but to heaven. In First Corinthians 6:9-10 Paul wrote, “Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God.” What is it that they will not inherit? It seems to be heaven as opposed to the church in this passage. Even though the church will be in heaven, Paul seems to be saying that those who practice these behaviors will not make it to heaven. Another passage is Galatians 5:19-21 which lists the works of the flesh; after this, Paul says, “I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God.” Ephesians 5:5 states, “For you may be sure of this, that everyone who is sexually immoral or impure, or who is covetous (that is, an idolater), has no inheritance in the kingdom of Christ and God.” In 2 Timothy 4:18 the apostle Paul writes, “The Lord will rescue me from every evil deed and bring me safely into his heavenly kingdom. To him be the glory forever and ever. Amen.” Peter also uses the term kingdom in this way; in 2 Peter 1:11, he writes, “For in this way there will be richly provided for you an entrance into the eternal kingdom of our Lord and Savior Jesus Christ.”
There are many other passages where the word kingdom is referring to the church, but in these few, the word kingdom can mean “heaven” instead.