Psalm 87, a  psalm by the sons of Korah the Levites, is joyful song celebrating Jerusalem,  the City of God, called Zion on holy Mount Moriah. The Lord has set deep his  foundations on Mount Moriah and surrounded the city of Jerusalem with walls and  gates. This is the city God loves. This is the city where God dwells. (Psalm  43:3; Psalm 48:1; Psalm 99:9) 
                              Not only is  Jerusalem honored by Israel and the Lord, but other great cities and lands  proclaimed Jerusalem’s greatness. The great cities that honored Jerusalem  included: 
                              
                                - Babylon,  the great city to the east
 
                                - Egypt  (Rahab), the great land to the south
 
                                - Philistia,  the neighbors to the west
 
                                - Tyre,  the great commercial center to the north
 
                                - Cush,  the powerful land far to the south of Egypt
 
                               
                              Citizenship  of a city could be attained by being born in that city. Then, the patron deity  of the city would provide protection for the citizens and exemption from taxes  and forced labor. So, likewise, in Psalms 87:4b-6 the focus is on Jerusalem  being the city of birth of these favored ones who can claim to have citizenship  in Jerusalem.  
                              But, also, in  this song of the Great City, the Most High who established Jerusalem will also  register the peoples from Babylon, Egypt, Philistia, Tyre and Cush as citizens!  These new citizens will make music and sing gladly because they know that all  God’s fountains (or, his sources of blessings) are found in this great city.  These foreigners have been welcomed as citizens into the Lord’s great and  eternal city.  | 
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