Following are a number of back-translations as well as a sample translation for translators of Jeremiah 51:3:

• Kupsabiny: “Do (plur.) not allow/grant the soldiers of Babylon
  the chance to bend their bows,
  nor to put on their clothes for battle.
  Do (plur.) not spare/have mercy on its young people,
  but destroy them completely.” (Source: Kupsabiny Back Translation)
• Hiligaynon: “They no longer give an opportunity the archers of Babilonia to be able to use their bows or their spears. They will- not ever -spare/leave any young men. They will- completely -destroy the entire soldiers of Babilonia.” (Source: Hiligaynon Back Translation)
• English: “I will tell them, ‘Do not allow the archers of Babylon to have time to put on their armor
  or draw their bows.
  Do not spare the young men of Babylon.
  Completely destroy their army.’” (Source: Translation for Translators)