Saint Paul identifies the communion of saints in Heaven as “Jerusalem” and as our mother: “But that Jerusalem which is above is free, which is our mother” (Galatians 4:26, D-R).
This is another reason why Catholics refer to the Church as the New Jerusalem and as Holy Mother Church. When Catholic priests, monks, and nuns chant the 150 Psalms of David, they often mentally apply the meaning of “Heaven” or “Church” to those passages that refer to “Jerusalem.” Saint Paul’s use of allegory in Galatians serves as an interpretive key to reading the Old Testament in a spiritual way.
In the Psalms, Jerusalem = Heaven. David = Christ. Sufferings of David = Sufferings of Christ. Sacrifice = the Mass. Thanksgiving = Eucharist. Priests = Priests. This makes the Psalms one of the most Christological books on the Old Testament and they very heart of New Testament worship.
Below are the various titles of Jerusalem in the Old Testament.
1. The city of David 2 Sam. 6:12
2. The city of the great king Matt. 5:35
3. The holy city Isa. 48:2; 52:1; Matt. 4:5
4. Salem, which means “peace” Gen. 14:18
5. The city of God Ps. 46:4; 48:1; 87:3
6. The city of the Lord of hosts Ps. 48:8
7. The city of righteousness Isa. 1:26
8. The city of truth Zech. 8:3
9. The city of the Lord Isa. 60:14
10. The perfection of beauty Lam. 2:15
11. The joy of the whole earth Lam. 2:15
12. The Lord our righteousness Jer. 23:6; 33:16
13. The Lord is there Ezek. 48:35
14. Ariel, the hearth of God Isa. 29:1