Conversation so far:
What role do priests play in Mandaeism?
There is a strict division between Mandaean laity and the priests.
What are the three grades of priesthood in Mandaeism?
There are three grades of priesthood in Mandaeism: the tarmidia disciples, the ganzibria treasurers and the rišamma leader of the people.

Question: How does one become a priest?
Self-contained rewrite: How does one become a priest in Mandaeism?