First Corinthians 15:24 says that at the end, that is, at the end of the millennium, when Christ will have destroyed all the power of Satan, He will deliver up the kingdom to God. This proves that after the millennium, during the time of the new heaven and the new earth, the kingdom of God will still exist. Therefore, the new heavens and the new earth in the future are also a part of the kingdom of God.
Therefore, according to the Scriptures, the kingdom of God stretches from eternity to eternity, without beginning and without ending. It is very wide in its scope. The kingdom of the heavens, which has a beginning and an ending, is a part of the kingdom of God, but its scope is narrower. Before the kingdom of the heavens began, there was already the kingdom of God. After the kingdom of the heavens ends, the kingdom of God will continue to exist for eternity. During the time of the kingdom of the heavens, the kingdom of the heavens is the kingdom of God. Therefore, sometimes the kingdom of the heavens is also called the kingdom of God.
Matthew 19:23-24 shows that the kingdom of the heavens is the kingdom of God. Matthew 13:31-33; 11:11; and 8:11 compared with Luke 13:18-21; 7:28; 13:28-29 prove also that the kingdom of the heavens is the kingdom of God. Since the kingdom of the heavens is a part of the kingdom of God, it can also be called the kingdom of God. Because California is a part of the United States, it can also be called the United States. For example, a foreign visitor who comes to California also comes to the United States. Although California can be called the United States, the United States cannot be called California. Likewise we may call the kingdom of the heavens the kingdom of God, but we cannot call the kingdom of God the kingdom of the heavens. This is because the kingdom of God embraces the kingdom of the heavens, but the kingdom of the heavens does not embrace the kingdom of God.
The kingdom of God is His entire ruling from eternity to eternity. The kingdom of the heavens is the ruling of the heavens from the birth of the church to the end of the millennium. Whoever is in the kingdom of the heavens is in the kingdom of God. But all those in the kingdom of God may not necessarily be in the kingdom of the heavens. All of the saved ones are in the kingdom of God and all enter into the kingdom of God, but they may not all enter into the kingdom of the heavens. Only the overcoming believers participate in the reality of the kingdom of the heavens and will be able to enter into the manifestation of the kingdom of the heavens. This is the difference between the kingdom of the heavens and the kingdom of God.