Albert Barnes Commentary Psalms 102:21

"That men may declare the name of Jehovah in Zion, And his praise in Jerusalem;" — Psalms 102:21 (ASV)

To declare the name of the Lord in Zion ... - That his name might be declared in Zion, or that his praise might be set up in Jerusalem again. That is, that his people might be returned there, and his praise be celebrated again in the holy city.