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