The Great Treasure, or Genza Rabba, is the sacred work most revered by the Mandaeans, the last surviving Gnostic sect from the period of late antiquity, who reside today in southern Iraq, the adjacent regions in Iran, and in a growing diaspora throughout the world. This work, an eclectic conglomeration of moral teachings, wisdom literature, creation myths, polemics, liturgy, and other such genres, is composed in Mandaic, an ancient Aramaic dialect closely related to Syriac and the language of the Aramaic portions of the Babylonian Talmud. Traditionally divided into two volumes, Right and Left, and into eighteen tractates, it probably assumed its current form in the 7th century, although colophons within it indicate that its oldest portions date to the end of the 2nd century CE.

The Petermann edition remains the only critical edition of this text, the basis for which is a 16th-century manuscript in the Bibliothèque Nationale, Paris. The first volume contains the entire text of the Great Treasure, and the second contains corrections and emendations on the basis of three other manuscripts from the same collection. Originally released one hundred and forty years ago in a limited edition of 100 copies, this edition subsequently became the chief reference for the study of the work in its original language. For the first time since 1867, this essential text is once again available for all scholars of Middle Eastern literature and of the history of religions, particularly Gnostic traditions such as Mandaeism. This Gorgias Press edition includes a new introduction by Charles Häberl.

Julius Heinrich Petermann (1801-1876) was a German Orientalist and Professor of Oriental Literature at the University of Berlin. He achieved distinction as the only western scholar of his time familiar with the traditional interpretation of the Mandaean literature, acquired during the time he spent travelling through the Middle East on behalf of the King of Prussia. In addition to his account of these travels, he is chiefly known for his work on Samaritan and Armenian.