The Parthian Empire was based on a loosely configured system of vassal kings. The lack of rigidly centralized rule over the empire had drawbacks, for instance, allowing the rise of a Jewish robber-state in Nehardea (see Anilai and Asinai). Yet, the tolerance of the Arsacid dynasty was as legendary as that of the first Persian dynasty, the Achaemenids. One account suggests the conversion of a small number of Parthian vassal kings of Adiabene to Judaism. These instances and others show not only the tolerance of Parthian kings, but are also a testament to the extent at which the Parthians saw themselves as the heir to the preceding empire of Cyrus the Great. So protective were the Parthians of the minority over whom they ruled, that an old Jewish saying tells, "When you see a Parthian charger tied up to a tomb-stone in the Land of Israel, the hour of the Messiah will be near".