In the Book of Kings (one of the ‘books’ (originally, scrolls) of the Hebrew Scripture, part of the Christian ‘Old Testament’), ‘Zion’ is given as another name for the whole city of Jerusalem (1 Kings 8:1). Mt. Zion (or Sion) is the hill in Jerusalem upon which the temple sat (now occupied by a Mosque with the nearby ‘wailing wall’ as the only remnant of the temple (which itself was razed and rebuilt a few times over the centuries)).
Many of the psalms (in the Book of Psalms) were the hymns of their time used in worship, especially in the feasts of the Temple (on Mt. Zion in Jerusalem). And so, many of the psalms make reference to the Temple. But rather than keep saying ‘the temple this’ and ‘the temple that,’ the psalms used ‘Zion’ as a synonym or reference to the temple. “Send thee help from the sanctuary, and strengthen thee out of Zion” (Ps 20:2)
Isaiah uses ‘Zion’ as a center point for the LORD to establish his rule for Israel and all nations: Isaiah 2:3 “And many people shall go and say, Come ye, and let us go up to the mountain of the LORD, to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: for out of Zion shall go forth the law, and the word of the LORD from Jerusalem.”
You might recognize from Handel’s Messiah: Isaiah 40:9 – “O Zion, that bringest good tidings, get thee up into the high mountain; O Jerusalem, that bringest good tidings, lift up thy voice with strength; lift it up, be not afraid; say unto the cities of Judah, Behold your God!”
Zion is not so much a time of past paradise (though it represents a time of the past glory of the Davidic Kingdom) but a place where a future paradise will be established (reminiscent of the paradise lost of Eden): Isaiah 51:3 – “For the LORD shall comfort Zion: he will comfort all her waste places; and he will make her wilderness like Eden, and her desert like the garden of the LORD; joy and gladness shall be found therein, thanksgiving, and the voice of melody.”
And so, Zion is a symbol of the gathering of the scattered tribes of Israel united again politically in the restored covenant of the Davidic kingship. Thus the mid-20th century ‘Zionist’ movement of creating a Jewish state.
And also, Zion is used by Christians as an eschatological promise of paradise/heaven which comes from the Messianic prophecy of Isaiah where ‘all nations’ (even the Gentiles) will be gathered to worship God because of how Jesus, the Son of David, is able to restore and perfect all of the covenants made to the Israelites.
Zionara, -m