The holy city Jerusalem means that new church in regard to its teachings. That is why it was seen coming down from God out of heaven, because the only source of genuinely true teaching is through heaven from the Lord. It is because the city New Jerusalem means the church in regard to its teachings that it says “prepared as a bride adorned for her husband” (Revelation 21:2) and then,
One of the seven angels came to me and talked with me, saying, “Come, I will show you the bride, the wife of the Lamb.” And he carried me away in the spirit to a high mountain, and showed me the great city, the holy Jerusalem, coming down out of heaven from God. (Revelation 21:9, 10)
It is common knowledge that the bride and wife mean the church and the Bridegroom and Husband mean the Lord. The church is the bride when it is willing to receive the Lord and is the wife when it does receive him.
We can see that the Husband means the Lord in this passage because it says “the bride, the wife of the Lamb.
from The Lord, Section 63