Following are a number of back-translations as well as a sample translation for translators of Isaiah 9:3:

• Kupsabiny: “God, you will give those people happiness,
  make them rejoice very much.
  They are happy for what you will do to/for (them),
  like when people rejoice at the harvest,
  or like when the plunder is divided.” (Source: Kupsabiny Back Translation)
• Newari: “You have enlarged that nation,
  and you have also increased their joy. Rejoicing like people
  when they gather grain, and rejoicing like when they bring plunder
  and distribute the goods.” (Source: Newari Back Translation)
• Hiligaynon: “LORD, you (sing.) will-give them very great joy. They will-rejoice in your (sing.) presence like the people who rejoice at harvest-time or like the people who rejoice in the dividing-up the properties which they took-by-force from war.” (Source: Hiligaynon Back Translation)
• English: “Yahweh, you will cause us people in Israel to rejoice;
  we will become very happy.
  We will rejoice about what you have done
  like people rejoice when they harvest their crops,
  or like soldiers rejoice
  when they divide up among themselves the things that they have captured in a battle.” (Source: Translation for Translators)