Isaiah 65-66 gives the book's final answer to the communal lament: the Lord distinguishes true servants from rebels, promises new heavens and a new earth, receives humble worship, comforts Jerusalem, gathers all nations, and warns that final worship cannot be separated from final judgment.
Read and follow along: https://orthodoxbiblestudy.com/bible-studies/old-testament/isaiah/isaiah-65-66-new-heavens-new-earth-and-final-worship