I took this part from the article “Iranian society in the Sasanid period”/ by: Hassan Karimian / Current Research in Sasanian Archaeology, Art and History
Out of the other groups who were among this class at the end of the Sasanian period were the ayyaran or stalwarts. They were known for their manliness and generousity. They defended the oppressed againsr the oppressions and were blamed for being followers of Maani, the man who claimed to be a prophet and who demanded equality of all people in society and the removal of class discrimination (Nafisi 1367:130). The people of this class had independent fire-temples and their most important fire-temple was at Rivand near Sabzivar (Khurasan provine) and was known as Azar Barzenmihr (Pigulevskaia 137)). The people of this class believed that Zoroaster brought fire from sky (Muller 1363: 76). The heads were drawn from nobility and assigned directly by the king and their responsibility was to collect taxes (Pigulevskaia 1367:81). Therefore, the financial offices of the regions were under their jurisdiction (Ivanov 1358).
Please also note, this tradition was also practiced by Sasanid soldiers and were well back from Parthian times. This tradition survived centuries after Islam up to Mashrooteh. Interested readers can refer to Mohsen Zakeri’s book: Sasanid soldiers in early Muslim society: The origins of Ayyaran and Futuwwa [Paperback]