Mandaeism or Mandaeanism (Arabic: mndy'y@ Manda'iyah) is a gnostic religion with a strongly dualistic worldview. Its adherents, the Mandaeans, revere Adam, Abel, Seth, Enos, Noah, Shem, Aram, and especially John the Baptist. The Aramaic manda means "knowledge", as does Greek gnosis. According to most scholars, Mandaeaism originated sometime in the first three centuries AD, in Mesopotamia.
Priests and laymen
There is a strict division between Mandaean laity and the priests. According to E.S. Drower (The Secret Adam, p. ix):  [T]hose amongst the community who possess secret knowledge are called Nasuraiia--Nasoreans (or, if the emphatic <s> is written as <z>, Nazorenes). At the same time the ignorant or semi-ignorant laity are called 'Mandaeans', Mandaiia--'gnostics.' When a man becomes a priest he leaves 'Mandaeanism' and enters tarmiduta, 'priesthood.' Even then he has not attained to true enlightenment, for this, called 'Nasiruta', is reserved for a very few. Those possessed of its secrets may call themselves Nasoreans, and 'Nasorean' today indicates not only one who observes strictly all rules of ritual purity, but one who understands the secret doctrine.  There are three grades of priesthood in Mandaeism: the tarmidia "disciples" (Neo-Mandaic tarmidana), the ganzibria "treasurers" (from Old Persian ganza-bara "id.," Neo-Mandaic ganzebrana) and the risamma "leader of the people." This last office, the highest level of the Mandaean priesthood, has lain vacant for many years. At the moment, the highest office currently occupied is that of the ganzebra, a title which appears first in a religious context in the Aramaic ritual texts from Persepolis (c. 3rd century BCE) and which may be related to the kamnaskires (Elamite <qa-ap-nu-is-ki-ra> kapnuskir "treasurer"), title of the rulers of Elymais (modern Khuzestan) during the Hellenistic age. Traditionally, any ganzebra who baptizes seven or more ganzebrana may qualify for the office of risamma, though the Mandaean community has yet to rally as a whole behind any single candidate.  The contemporary priesthood can trace its immediate origins to the first half of the 19th century. In 1831, an outbreak of cholera devastated the region and eliminated most if not all of the Mandaean religious authorities. Two of the surviving acolytes (sgandia), Yahia Bihram and Ram Zihrun, reestablished the priesthood on the basis of their own training and the texts that were available to them.  In 2009, there were two dozen Mandaean priests in the world, according to the Associated Press.
What role do priests play in Mandaeism?
There are three grades of priesthood in Mandaeism:
There are three grades of priesthood in Mandaeism: