Following are a number of back-translations as well as a sample translation for translators of Isaiah 41:23:

• Kupsabiny: “Let (them) just say what is coming the day after tomorrow,
  so it can be known that they have power like God.
  Let them do go or bad
  for us to see if we should be afraid
  and be trembling!” (Source: Kupsabiny Back Translation)
• Newari: “Now tell us information of what is going to happen,
  From that we may be able to learn [whether] you really are a god.
  Do something, anything, good or bad,
  that will make us terrified and make us live in fear.” (Source: Newari Back Translation)
• Hiligaynon: “You (plur.) come-near and tell us (excl.) what will-happen in the future. Tell us (excl.) what have- you (plur.) -spoken before that will-happen so-that we (excl.) can-think if this was-fulfilled. Tell us (excl.) what will-happen in the future so-that we (excl.) will-know that you (plur.) are gods. You (plur.) do good-(thing) or bad-(thing) so-that we (excl.) will-be-amazed and terrified of you (plur.).” (Source: Hiligaynon Back Translation)