Charles Ellicott Commentary Isaiah 66:10

"Rejoice ye with Jerusalem, and be glad for her, all ye that love her: rejoice for joy with her, all ye that mourn over her;" — Isaiah 66:10 (ASV)

Rejoice you with Jerusalem ... —The holy city is still thought of as a mother rejoicing in her new-born child; friends and neighbours (that is, the nations friendly to Israel) who had shown pity for her sufferings are now invited to participate in her joy.