Following are a number of back-translations as well as a sample translation for translators of Proverbs 10:18:

• Kupsabiny: “A person who conceals/hides inside things/words of envy, is lying/deceiving,
  but also the one who goes around slandering is a fool.” (Source: Kupsabiny Back Translation)
• Newari: “Those who hide hatred in their hearts
  are liars.
  And those who keep on spreading lies
  are fools.” (Source: Newari Back Translation)
• Hiligaynon: “The man who hides his anger (is a) liar, and the ones-who are-slandering/gossiping (are) foolish.” (Source: Hiligaynon Back Translation)
• Kankanaey: “The liars, they conceal their hatred, and one who relates- a destructive -story is a fool.” (Source: Kankanaey Back Translation)
• English: “Those who will not admit that they hate others are liars,
  and those who slander others are foolish.” (Source: Translation for Translators)