Following are a number of back-translations as well as a sample translation for translators of Isaiah 51:6:

• Kupsabiny: “Raise (plur.) up the eyes to look to heaven
  and also look at the earth.
  Heaven shall perish
  and down here on earth shall end like a cloth.
  Those that live there shall die like flies,
  but the life that I bring will stay forever
  and the righteousness that I give shall never come to an end.” (Source: Kupsabiny Back Translation)
• Newari: “You are to set your eyes on the sky above,
  and to look at the earth below.
  The sky will be disappearing like smoke.
  And the earth will be torn like old cloth.
  The people on earth will die like flies.
  But my salvation will exist forever.
  My righteousness will never end.” (Source: Newari Back Translation)
• Hiligaynon: “You (plur.) look-at the heavens and the earth. The heavens will-vanish like smoke, and the earth will-be-rotten/wear-out like a cloth, and its residents will-die like (small)-insects. But the salvation which I will-give will-continue without end. The victory with righteousness that comes from me will-be yours (plur.) forever/[lit. until whenever].” (Source: Hiligaynon Back Translation)