Following are a number of back-translations as well as a sample translation for translators of Jeremiah 4:28:

• Kupsabiny: “So, the land/earth here below shall mourn
  and darkness shall cover the sky.
  I God have decided decisively
  and I shall not go back on it.’” (Source: Kupsabiny Back Translation)
• Hiligaynon: “The earth will-mourn and the heavens will-be-darkened, for I have- already -spoken the punishment, and I will- no longer -take- it -back. I have-decided already and my mind/[lit. thinking] will- no longer -change.’” (Source: Hiligaynon Back Translation)
• English: “I will do to my people what I said that I would do,
  and I will not change my mind.
  So when that happens, it will be as though the earth will mourn
  and the sky will become very dark.’” (Source: Translation for Translators)