Following are a number of back-translations as well as a sample translation for translators of Isaiah 49:4:

• Kupsabiny: “Then I said, ‘But I have worked in vain.
  I have struggled in vain and there is nothing.
  But God shall give me what is due to me/what I deserve,
  God will do justice to me for the things I am doing.’” (Source: Kupsabiny Back Translation)
• Newari: “But I said, "I worked hard but it was useless.
  The work I have done by [my] strength is useless.
  Yet what may be for me, that is in the LORD’s hand.
  The reward of that is with God.” (Source: Newari Back Translation)
• Hiligaynon: “But I said, ‘My hard-work has no value; I wasted my strength for nothing.’ But I just hand- this -over to the LORD my God; he will-be- the -one-to-pay-back what I have-done.” (Source: Hiligaynon Back Translation)