Eusebius of Caesarea

Zion and Jerusalem, that here have the good news told them, the apostle knew to be heavenly, when he said, "But the Jerusalem that is above (that is, our mother) is free," and, "You have drawn near to Mount Zion and the city of the living God, heavenly Jerusalem and to an innumerable company of angels." Zion might also mean the church established by Christ in every part of the world, and Jerusalem the godly citizenship (politeuma) that, once established long ago among the ancient Jews alone, was driven out to the wilderness by their impiety and then again was restored far better than before through the coming of our Savior. Therefore, the prophecy says, "Let the waste places of Jerusalem break forth into joy together, for the Lord has pitied it and saved Jerusalem."Nor would you be wrong in calling Zion the soul of every holy and godly person, so far as it is lifted up above this life, having its citizenry in heaven and seeing things far beyond the world. For it means "a watchtower." And insofar as such a person remains calm and free from passion, you could call him Jerusalem—for Jerusalem means "vision of peace."