Following are a number of back-translations as well as a sample translation for translators of Proverbs 26:19:

• Kupsabiny: “A person who deceives another person and then says he was joking,
  is like a crazy person who plays with sharp weapons.” (Source: Kupsabiny Back Translation)
• Newari: “People who deceive others and say
  "I was only joking"
  are like madmen holding torches
  and dreadful bows and arrows.” (Source: Newari Back Translation)
• Hiligaynon: “A man who cheats his fellowman, and then he says that was just a joke, he is like a mad/[lit. bad head] man who shoots a blazing bow-and-arrow that can-kill.” (Source: Hiligaynon Back Translation)
• Kankanaey: “is the one who deceives his companion then he says that it was a (lit. his) joke.” (Source: Kankanaey Back Translation)
• English: “are as foolish as those who deceive someone else
  and then say, ‘I was only joking.’” (Source: Translation for Translators)