The question of how Imam Reza entered and then settled in Marv, the capital of Islamic caliphate under Abbasid Ma’mun, has raised various hypotheses, specifically centered around some of the important personages of that era. Fazl bin Sahl, surnamed Zhur-Riyasatayn (literally: owning two presidencies), has been mentioned variously with different or even paradoxical analyses regarding Imam’s vicegerency and other important issues. It seems that to achieve a comprehensive and logical comprehension of issues related to Imam Reza, Ma’mun and his court, it is necessary to scrutinize Dhur-Riyasatayn&rsquo
