Following are a number of back-translations as well as a sample translation for translators of Jeremiah 9:8:

• Kupsabiny: “Their tongues are like poisoned arrows,
  that like to deceive.
  Each one flatters (oils the mouth) when he speaks to his neighbor
  but in his stomach, he prepares stumbling blocks.” (Source: Kupsabiny Back Translation)
• Hiligaynon: “For their tongue is like a deadly bow-and-arrow, which is purely deception what they are-talking. They speak good towards their fellowman, but inside their heart they plan to harm them.” (Source: Hiligaynon Back Translation)
• English: “What they say injures people like poisoned arrows do.
  They say to their neighbors, ‘I hope things will go well for you,’
  while they are planning to kill them.” (Source: Translation for Translators)