Following are a number of back-translations as well as a sample translation for translators of Proverbs 25:26:

• Kupsabiny: “If/When a righteous person agrees with/joins a sinner it is like water that has been contaminated or like a well which poison has been poured from.” (Source: Kupsabiny Back Translation)
• Newari: “A righteous person who joins in with wicked people
  is like water into which dirt has been thrown.” (Source: Newari Back Translation)
• Hiligaynon: “A righteous man who agrees with a wicked man is like a muddied spring or a dirty well.” (Source: Hiligaynon Back Translation)
• Kankanaey: “If a righteous-person gives-in-to what a sinful-person says, it is like a clean spring or water-source (lit. place-of-fetching-water) in-which-is-placed something-dirty.” (Source: Kankanaey Back Translation)
• English: “When a righteous/good person gives in/yields to wicked people,
  that is as bad as a spring that becomes muddied or a fountain that becomes polluted.” (Source: Translation for Translators)