Psalms 102:21

To declare the name of the LORD in Zion, and his praise in Jerusalem;

The verse makes known anew God's plan for the salvation of the heathen, which had been almost wholly lost sight of in the years following the occupation of the Promised Land. That declaring of the name of the Lord in Zion and His praise in Jerusalem fulfills the Lord looking down from the height of His sanctuary in heaven upon the earth to hear the groaning of the prisoner and to loose those appointed to death. It takes place when peoples and kingdoms, the nations, are gathered together to serve the Lord.

Its meaning is that the knowledge of God's name and His praise will be declared and spread in Zion and Jerusalem among those gathered peoples. As a result a people yet to be created shall praise the Lord, and the heathen and all the kings of the earth shall fear His name and glory.