The initiation of a Perso-Aryan child into the Aryan community (Av. airyaman-) is known as the second birth. The ceremony of the initiation consists of the investiture of the child with a sacred girdle and sacred shirt.
Here is a school treatise about the significance of the ceremony of the initiation, originally written in Pārsīg (the so-called Pahlavi) and belonging to the Sasanian Period:
Treatise about the Significance of the Sacred Girdle
Text, Transcription an Translation
By Raham Asha
The K.R. Cama Oriental Institute
Mumbai, 2005
Here is a school treatise about the significance of the ceremony of the initiation, originally written in Pārsīg (the so-called Pahlavi) and belonging to the Sasanian Period:
Treatise about the Significance of the Sacred Girdle
Text, Transcription an Translation
By Raham Asha
The K.R. Cama Oriental Institute
Mumbai, 2005