His work on earth was to establish it, Matthew 3:2.

It embraces all who by the Spirit of Christ are united to him as their divine Head and King, to love, serve, and enjoy him for ever. It has indeed its outward form, the visible church, Matthew 13:47, and bestows on the world the richest of temporal blessings but its true dominion is in the souls of men. They afterwards learned that his kingdom was not of this world, John 18:36-37 that its origin, spirit, means, and ends were spiritual and heavenly. Hence the contests among his disciples, ere they had fully learned Christ, about precedency in his kingdom and hence probably the sons of Zebedee desired the two chief places in it, or those nearest to their endeared Master and Lord. The Jews, overlooking the spiritual import of this language, expected the Messiah to appear as a temporal king, exercising power over his enemies, restoring the throne of David to all its splendor, subduing the nations, and rewarding his friends and faithful servants in proportion to their fidelity and services. The ancient prophets, when describing the character of the Messiah, Daniel 2:44 7:13,14 Micah 4:1-7, and even when speaking of his humiliation and sufferings, were wont to intersperse hint of his power, his reign, and his divinity. American Tract Society Bible Dictionary ДЄn expression used in the New Testament to signify the reign, dispensation, or administration of Jesus Christ. The members of the 'invisible church' are citizens of the kingdom of heaven. At 'the end' Christ is to deliver up to the Father the mediatorial kingdom that he received at his ascension, Ephesians 1:20, after having reigned and put down all rule, authority, and power, and all enemies under his feet, 1 Corinthians 15:24 and the kingdom of God, without distinction of persons, shall be complete and forever. The kingdom is to be fully manifested at the coming of Christ, the Son of man. The disciples went everywhere preaching the word of grace, 1 Thessalonians 2:12, and persuading men to enter the kingdom by faith and holiness. He laid the foundations of it on the day of Pentecost by the outpouring of the Holy Spirit, and rules it from his throne in heaven. He declared that the time of its manifestation was known only to the Father. He taught its mysteries to the disciples, especially after his resurrection, Acts 1:3 and sent them forth to preach it. Luke 1:32, but was rejected, and took the kingdom from Israel. Jesus Christ preached it, Matthew 4:17 explained its character and demands, as, for instance, that its citizens must be holy, meek, Christlike, etc., that when established it will be a condition of peace, purity, and glory, Matthew 25:34 Mark 9:47 Acts 14:22 Christ came as the King to Jerusalem. The prophets foretold its restoration, Daniel 12:7-13 Psalms 2:1-12 Isaiah 2:1-22 Micah 4:1-13 Jeremiah 23:5 Ezekiel 34:23 John the Baptist came to announce it. The kingdom ceased as a visible power, with the loss of its inner spirit, when the nation lapsed and persisted in idolatry. He made the kingship visible in David, 1 Samuel 16:1-23, and permanent in bis family. God reestablished it in Israel, taking the kingship himself. From the moral kingdom the earth has revolted. The power and glory of the divine kingdom are shown in a measure in creation and providence. The kingdom of God is perfectly established in the heavens. 2, the condition of things Christ came to explain, Luke 1:33 Acts 1:3, and to bring on earth, Matthew 4:17 Matthew 3:1-17, Christ's rule over Israel, Matthew 21:13 Matthew 4:1-25, the rule that God offered or committed to Israel, Matthew 21:43 1 Chronicles 17:14 1 Chronicles 5:1-26, the state of things in the history of the church during the conflict on earth of the so-called kingdom of grace, preparatory to the kingdom of glory, Matthew 13:1-58 Matthew 6:1-34, Christ's rule in spiritual and eternal righteousness over the redeemed earth, Revelation 12:10, in contrast with the world-powers, Daniel 7:18 then the kingdom will destroy and take the place of the four monarchies, Daniel 7:1-28, and have its glorious manifestation 7, the visible glory of Christ, Matthew 16:28 Matthew 8:1-34, the rule of God the Father over earth and heaven, Matthew 6:10 Matthew 9:1-38, the heavenly state. These terms describe: 1, a life of righteous allegiance to Christ, entered by faith, lived by love, and crowned with glory, Matthew 6:33, etc.

2 American Tract Society Bible Dictionary.

The kingdom of heaven wiki