"sleep the sleep of the just"

[Alan Baragona]

Does anyone know the origin of the phrase "sleep the sleep of the just"?  It's not biblical or Shakespearean, it's not in Barlett's or The Oxford Dictionary of Quotations or several other dictionaries of quotations and phrases that I've checked.  "Ecclesiastes" says "the sleep of the labouring man is sweet," but that's as close as I can find to the sentiment, and it's not very close to the wording.

Alan Baragona