Zion is the name of a prominent mountain in the southern portion of Jerusalem in Isaiah’s day. It stood for the heart and center of the city.
Jerusalem was called the city of peace, the city of David, the city of God, and in that respect, peace is result of doctrine or truth which is from God, and Zion being the heart of the city being the mountain of Gods vast truth, which is the substance of the city.
Therefore, Zion is synonymous with the believers, or better stated, mature believers in Christ.
They are the heart and soul of believers that have arrived at a completion of their lives.
Converts, ‘shuwb,’ is a reference to some but not all believers returning from captivity. That is some but not all believers would return to Jerusalem.
So it has a triple meaning here. When Jerusalem is restored in Daniels day, some but not all Israelites would return. Likewise, when Christ returns at the Second Advent, some but not all believers that had been in hiding during the Tribulation, would return to the city. They will be the remnant from which the population of the world will be restored.
And last, some but not all believers will arrive at maturity in their individual spiritual lives.
Redeemed, ‘padah,’ is a term that implies the return from captivity, from danger, from slavery and so forth. This return comes with a price paid in the form of a purchase or a ransom.
Judgment, ‘mishpat,’ means the application of justice.
Righteousness, ‘tsadaqah,’ is the reference to the character of those who will return or be freed.
Therefore, Zion, or all believers by reference to truth, shall be purchased out of slavery and captivity (from sin), by means of a purchase of a ransom, paid as a price demanded by sin. And, they will return not as slaves, but as free people, no longer under the oppression of evil.
When the Jewish people returned back in Daniels day, it was again yet another picture symbolizing the salvation principle of Christ’s work on the Cross for all believers (all who have and would believe in the Savior, who paid the price).
The reality came after the Cross, when Jesus Christ actually made that payment historically in time, and then the promise of the restoration of Israel at the Second Advent would again be the fulfillment of Gods promise to restore Jerusalem to Gods people, out of the hands of an evil world, thus establishing Gods kingdom our from the remnant, who are believers.
But not all will benefit from this overall principle.
Not all will believe. Unbelievers will remain in captivity or separated from God forever.
Not all believers will advance to maturity.
And not all believers in the Tribulation, will survive that terrible time in history.