'Jerusalem' means 'teaching of peace', so the 'New Jerusalem' is the new teaching of peace. 
- When the Hebrews removed leaven from their homes, they were not symbolically removing their sin, but removing the old teaching of the law in preparation for the teaching of peace. 
During the sermon on the mount, Jesus repeatedly said "You have heard it said... but I say...".  He was ushering in the new teaching of peace. The kingdom (teaching) of heaven was "at hand".  It was there in front of them in the teaching of Jesus.
- ↑ Heb 8:13 In that he saith, A new [covenant], he hath made the first old. Now that which decayeth and waxeth old [is] ready to vanish away.
- ↑ Heb 10:1 For the law having a shadow of good things to come, [and] not the very image of the things, can never with those sacrifices which they offered year by year continually make the comers thereunto perfect.
- ↑ Mt 5:21, 27, 33, 38, 43
- ↑ Kingdom at hand
|You are the temple
John says, "Re 3:12 Him that overcometh will I make a pillar in the temple of my God, ..." This is not literal, but a symbol. You are the temple of God. 
- Re 3:12 "...and he shall go no more out..." You can't leave the temple; you are his. 
Re 3:12"...and I will write upon him the name of my God" You will have the reputation of God. The word for 'heaven' shamayim שמים is 'the reputation שמ of creation י finished by the son ם. You are the reputation of God. You are the visible representative of the invisible God.
- ↑ 1Co 3:16 Know ye not that ye are the temple of God, and [that] the Spirit of God dwelleth in you?
- ↑ Joh 6:37 All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out.
|You are the reputation of God
When Moses return from the mountain with the law, and the people were worshiping a golden calf , God was going to destroy them all and start over with just Moses.  Moses interceded saying that the nations would deride God because he could not save his people. It was for God's reputation that they were spared. 
- His reputation is not important because of his ego. It is important because he wishes to be known. Anything that misrepresents God is counter to that purpose. This is why lying and gossip are so serious.
We are not spared because we are good people. We are spared because God's reputation is on the line. He is Holy; he is Love. Revealing the invisible God, is the message of the cross.
- ↑ Ex 32:4 And he received [them] at their hand, and fashioned it with a graving tool, after he had made it a molten calf: and they said, These [be] thy gods, O Israel, which brought thee up out of the land of Egypt.
- ↑ Ex 32:10 Now therefore let me alone, that my wrath may wax hot against them, and that I may consume them: and I will make of thee a great nation.
- ↑ Ex 32:12 Wherefore should the Egyptians speak, and say, For mischief did he bring them out, to slay them in the mountains, and to consume them from the face of the earth? Turn from thy fierce wrath, and repent of this evil against thy people.
The kingdom of heaven is the kingdom of the reputation of God, made through his work in finishing his creation. The New Jerusalem, the new teaching of peace, was the plan from the beginning. 
- The new teaching of peace came down from heaven , not physically from a high place to a low, but in his incarnation and condescension. God lowered himself so that we might be lifted up. Then he dwelt within us. His teaching is not in words only, but in the lives of his people.
He gives us a new name, a new reputation, that of God himself; we are holy, we are love. Our new name is Israel; man joined to God by revelation.
- ↑ Re 13:8 And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
- ↑ Re 21:10 And he carried me away in the spirit to a great and high mountain, and shewed me that great city, the holy Jerusalem, descending out of heaven from God,