John sees a new heaven and earth because the old had passed away and the sea was no more. Peter speaks of this in 2 Peter 3. Peter tells us that the old heavens and earth began with creation and ended with the Flood (2 Peter 3:5-6). Then, he speaks of the “now” heavens and earth which began with Noah and His family and was about to end in Peter’s day (1 Peter 4:7) at the desolation of Jerusalem (2 Peter 3:7-12; Isa. 66:7-9; 65:8-25; 66:22-24). At that time, the redeemed received their eternal reward (Luke 21:28, 31; Rev. 11:18; Matt. 25:46) and the spiritual kingdom reign of Christ began (the Millenium). The heavens and earth phrase does not refer to a literal earth and heaven but to distinct world systems and orders. One might even call them dispensations from the standpoint of God’s distinct differences in dealing with the human race.
John sees the Holy city, new Jerusalem, coming down outmof heaven from God, made ready as a bride adorned for her husband (21:2). This city is called the New Jerusalem, not the new Rome. The contrast is between the old earthly Jerusalem and the new heavenly Jerusalem (cf. Gal. 4:25-26).
Christ’s kingdom is compared to a celestial city (Lk. 21:28, 32-32; Heb. 12:28) that is described as being “holy” for in it dwells righteousness (2Peter 3:13). Nothing unclean or that makes an abominatin and lie will enter into it, but only those written in the Lamb’s book of life (21:27; cf. Isa. 65:17-25). This new city is a reference to those in His kingdom who are like a bride who has adorned herself for her husband (cf. Eph. 5:22-33). The Lamb would consummate this marriage relationship when he took his bride unto himself. The time must fit the visions that John received. They were to shortly take place (Matt. 19:4,5; 25:1-13; John 3:28-30; 14:1-3; 1 Thess. 4:13-18; 1 Cor. 15:50-58; Lk. 21:20, 27-33). The end of the age was during the first century. The end of the old and the start of the new occurred in that same century. When that end came, Jesus delivered the kingdom up to the Father not to end his reign, but to start it. The word “delivered” is the same one mentioned earlier in the text where Paul speaks of delivering that which he also preached (death, burial, and resurrection of Christ).  Paul didn’t quit that role when he delivered it at Corinth.  He continued to deliver it whereever he went.  At that time of the end, Jesus will present His bride to his Father. That’s the start of His reign with the saints and it is commensurate with the start of his marriage relationship. If we take the view that Jesus’ deliverance of the kingdom means he’s ending his reign, we have Jesus starting and ending at the same time and divorcing His new bride as soon as He consummates the new relationship. This makes no sense. Check out more blogs from this text.