Psalm 87, another Korahite psalm in the final cluster of Book III, is a song of Zion—yet a remarkably unusual one in that other nations are included in the ranks of Zion's citizenry. The Expositor's Bible Commentary, in its introductory note on this psalm, says that it's "difficult to postulate an original life-situation for the psalm. It may well have been associated with any of the three pilgrimage festivals, when Israel together with proselytes [from other nations] joined together in the worship of God at the temple." While there may have been some application for that time, the psalm when composed was clearly forward-looking—prophesying of the future. Thematically, this psalm follows David's remark in the previous psalm about all nations eventually coming to worship the true God (Psalm 86:9).

"The holy mountains" of Psalm 87:1, where sits the foundation of God's worship system and from where He will ultimately rule all nations, refers either to Israel and Judah or to the hills of Jerusalem. If the former, verse 2 narrows the focus to Zion. If the latter, verse 2 simply defines the mountains as those of Zion. "The Lord loves the gates of Zion" because they form the entrance to the temple through which His people have a relationship with Him. The Nelson Study Bible states that "the verb loves includes the idea of choice (see Deuteronomy 6:5) as well as emotion. God chose Jerusalem, and He also has an enduring affection for the city" (note on verses 2-3).

In verse 4, the end of the phrase "I will make mention of Rahab [i.e., Egypt (see Isaiah 30:7)] and Babylon to those who know Me" could be translated as "....AS those who know Me" (note on Psalm 87:4)—or perhaps "...AS OF those who know Me." The NIV renders verse 4 this way: "I will record Rahab [Egypt] and Babylon among those who acknowledge me—Philistia too, and Tyre, along with Cush [i.e., Ethiopia or perhaps all of east and southern Africa]—and will say, 'This one was born in Zion.'" This is saying that people born in other nations, even nations that were troublesome to Israel, will be considered as "born in Zion" once they repent and worship the true God. Verse 6 affirms, "The Lord will record, when He registers the peoples: this one was born there."

This process begins with the Church of God today: "But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem...to the general assembly and church of the firstborn who are registered in heaven" (Hebrews 12:22)—spiritual Zion according to the New Covenant, "the Jerusalem above...which is the mother of us all" (Galatians 4:26). The New Testament describes the gentile nations generally as "aliens from the commonwealth of Israel and strangers of the covenants of promise, having no hope and without God in the world" (Ephesians 2:12). Yet those who come into God's Church have a drastically changed status—to that of being "no longer strangers and foreigners, but fellow citizens with the saints and members of the household of God" (verse 19). Through Jesus Christ, they become "Abraham's seed, and heirs according to the promise" (Galatians 3:29).

Then, when Christ returns, these will all be spiritually born of Zion in the resurrection. As Isaiah 66:8 says: "Shall the earth be made to give birth in one day? Or shall a nation be born at once? For as soon as Zion was in labor, she gave birth to her children."

Afterward, God's holy mountain, His Kingdom, will grow from Zion to fill the entire earth—so that all nations will become part of Israel in a spiritual sense. All will be born in Zion. How marvelous is God's plan for all people! It is a cause for singing and rejoicing (Psalm 87:7). The phrase "all my springs are in you" (same verse), or "all my fountains are in you" (NIV), calls to mind the "river whose streams shall make glad the city of God" (Psalm 46:4), the life-giving river of the New Jerusalem (Revelation 22:1-5), the "fountain of life" (Jeremiah 2:13) and the "wells of salvation" (Isaiah 12:3), from which living water will be drawn with joy.

Occurring as it does near the end of Book III, which contains a number of psalms about Israel's devastation at the hands of enemy nations (previewing the time of the great tribulation ahead), perhaps this psalm was placed here to remind God's people to not focus on wishing ill on their enemies but to long for the day when all will be reconciled, dwelling happily together in the family of God.