Following are a number of back-translations as well as a sample translation for translators of Isaiah 41:26:

• Kupsabiny: “Which idol has shown these things beforehand
  so it can be said that he speaks the truth.
  No one has shown it beforehand
  and those words have not been heard.” (Source: Kupsabiny Back Translation)
• Newari: “Which of your gods has shown this from the beginning and made it possible for us to know?
  Who has shown this from the beginning and made it possible for us to say that it was right?
  No one has told us of this matter,
  No one has spoken a single word to us before.
  No one has heard the words that you spoke.” (Source: Newari Back Translation)
• Hiligaynon: “Who among you (plur.) have-told in the time-past that this will-happen so-that we (excl.) can-know and can-say that he is right? No one ever have-told you (plur.), and no one have-heard that you (plur.) said-something.” (Source: Hiligaynon Back Translation)