I've always believed (like Christians around me) that Christ's Bride is the church. However, I recently met two guys that claimed that the Bride is actually the new Jerusalem that comes down from Heaven in Revelation (3:12, 21:2, 21:10). What is the Biblical support for these two viewpoints?
The new Jerusalem that comes from heaven in Rev 19 is "prepared as a bride adorned for her husband." (emphasis added) However, I would understand why some might think that Jerusalem is Christ's bride. In the Old Testament, Israel (or Judah or Jerusalem) is described as God's wife:
For thy Maker is thine husband; the LORD of hosts is his name; and thy Redeemer the Holy One of Israel; The God of the whole earth shall he be called. For the LORD hath called thee as a woman forsaken and grieved in spirit, and a wife of youth, when thou wast refused, saith thy God. Isa. 54:5-6
Turn, O backsliding children, saith the LORD; for I am married unto you: and I will take you one of a city, and two of a family, and I will bring you to Zion: Jeremiah 3:14
This comparison is the whole purpose of the book of Haggai as well. It's a beautiful way to render God's relationship with his people.
Contrastingly, the imagery that we have with Christ and His Bride is that of a coming Bridegroom and a bride in preparation. As the angel shouts in Revelation 19:7
"Let us be glad and rejoice and give Him glory, for the marriage of the Lamb has come, and His wife has made herself ready."
Paul strengthens this image when he says in II Corinthians 11:2
...I am jealous over you with godly jealousy: for I have espoused you to one husband, that I may present you as a chaste virgin to Christ.
The two metaphors are not contradictory. Jesus uses many contrasting "I ams:" Jesus is the Lamb, the Door, The Good Shepherd, etc. All of them are helpful, but they are only pictures. HOWEVER, this imagery of Christ and His bride persists through all the New Testament, especially in the Revelation. It is meant to typify how an engaged virgin would wait for her promised husband to come for her. That is what Christians are doing today. God was never married to a city. Jesus is not coming back for a city. The city always was a symbol for the collective people of the city, and the Bride is a metaphor for all the Christ's body.
There's no reason why God couldn't use a "bride" analogy two places in different contexts. If one day I say, "Bob works as hard as a horse" and another day I say, "Charlie can run as fast as a racehorse", that's not a contradiction because I compare two different people to horses, or compare them in two different ways. Even if it's true that God refers to himself as having two different brides, that doesn't make him a bigamist! Neither is literal, it's just an analogy.
That said, New Jerusalem is to be the home of the saved. The Church is the collection of those who are saved. So both are pretty much the same group of people.
The Scriptures usually used to justify this assertion, come from the apocalypse (Revelation) chapter 21 verses 1 through 4 and 9and 10.
Rev 21 KJV
1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God.
4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
9 And there came unto me one of the seven angels which had the seven vials full of the seven last plagues, and talked with me, saying, Come hither, I will shew thee the bride, the Lamb's wife.
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,
However those assertions must be clothed in the fact that most of the Revelation is written in symbols, and many of us feel that was done because of the persecution of the Church at that time.
Using the city of Jerusalem as a symbol of the bride of Christ would be a well understood reference since Jerusalem was compared to a beautiful bride during the reigns of both King David and King Solomon. Both the new Jerusalem and the Bride of Christ were not meant to indicate the original things it should not be considered that the Bride of Christ meant the New Jerusalem per-se.