The Sasanian period

The Sasanian kingdom started as early as
He projected himself as heir of the (Kavi-)Achaemenian kingdom, thereby implying that he could restore the Aryan land (Pers. erān-šahr). Sāsān, eponym of the Sasanian dynasty, was reputed to have descended from a certain Sāsān son of Artaxšaçā «who is called Vohu-manah son of Spəņtōδāta. »
He entrusted Tōsar with the task of collecting and revising sacred texts, and reducing them to some sort of canon of scripture.
Tōsar
The priestly teacher Tōsar (third century A.D.) was himself of the royal-Parthian house who became Ardašēr’s counsellor and helped him to overthrow many local rulers and re-establish the Aryan kingdom in the Aryan land with undivided rule by a monarch. He collected many Avesta manuscripts and prepared a standard edition of the Avesta comprising 21 books as an authoritative text of the Daēnā. He also wrote treatises about both political and religious affairs. Rōzveh (Ibn al-Muqaffa˓) translated (with some interpolations) some of them into Arabic: Letter to Māhgušnasp king of Pedišxvārgar, Letter to the king of