Following are a number of back-translations as well as a sample translation for translators of Isaiah 65:18:

• Kupsabiny: “You shall be happy and always rejoice
  over the words/things that I am doing.
  I shall make Jerusalem have joy
  and its people will be made happy.” (Source: Kupsabiny Back Translation)
• Newari: “But [what] I created [is] a matter of joy and rejoicing forever — yes indeed!
  For I have made Jerusalem full of joy and the people there full of rejoicing.” (Source: Newari Back Translation)
• Hiligaynon: “Therefore you (plur.) be-glad and rejoice without end to what I will-do. For I will-make Jerusalem to be a delight of the people, and its people will- also -give joy.” (Source: Hiligaynon Back Translation)