The composer of this psalm was looking forward to the extension of the city of Jerusalem. It had been founded by God (v. 1) and he had shown special love towards it (v. 2). The special display of love was his decision to locate the temple and its worship within the city. There his people could gather together and worship him and have fellowship with one another. As the psalmist contemplated the city, he was encouraged by thinking about the many prophecies that had been given about its future increase (v. 3).
Where were the future inhabitants going to come from? The surprising answer to this question is that many of them would come from nations that had been traditional enemies of Israel. Egypt, here called Rahab, and Babylon had enslaved their forefathers. The Philistines had been a constant thorn in Israel’s experience down the centuries. Tyre had proved a fickle friend: under Hiram there had been friendly relations with David and Solomon, but those days were long in the past. Cush was a threat from the south.
An amazing feature of the ingathering of citizens of Zion was that each one of them would be born in her (vv. 4-5). Yet they experienced this without leaving their place of residence. The explanation of this aspect is that Zion progressed from being an earthly city to become a spiritual domain accessible from every place on earth. Zion would no longer be limited to a few square miles in the Middle East; instead it would become a heavenly entity, large enough to absorb millions of inhabitants. This is what happened with the coming of Jesus.
The Lord would establish the city by giving her many inhabitants. He himself functions as the registrar of the city, personally recording the names of the inhabitants when each of them enters it. Unlike earthly cities, there is not a record of those who leave it because none of them ever do. They are totally satisfied with what it provides (v. 7). The heavenly city is depicted as a place of joy, with singers and dancers all delighting to say that the source of their joy is the Lord who dwells in the heavenly Zion.
The message of the psalm is very encouraging. It reminds us that God rejoices to convert his enemies, then records them among his people, and provides them endlessly with spiritual blessings from his abundant resources.