As the first readers, the Messianic Jews, lived in Jerusalem, they knew Mount Zion all too well: that is where the temple stood and where God lived. With the earthly Zion you think of the temple city, Jerusalem. But now, at Mount Zion, they must look higher up, toward heaven: the city of the living God. That is where the living God lives: the God who lives and who gives life (compare the God of Zion in Psalm 84:7). He is the God who speaks, acts, liberates, reacts, and amends.
22 But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem, and to innumerable angels in festal gathering,