Cantera, Alberto. 2013. Talking with god: The Zoroastrian ham.paršti or intercalation ceremonies. Journal Asiatique 301(1). 85–138.
Read the article here or here. Abstract:
Among the different variants of the Zoroastrian long liturgy attested in the manuscripts we find two in which a coherent text in Young Avestan is divided into sections that are intercalated between the central part of this ceremony, the recitation of the Old Avestan texts. They are the Widēwdād and Wištāsp Yašt ceremonies. Usually they are considered late compositions in which the long liturgy has been extended artificially through the intercalation of of already exiting Young Avestan texts without any relationship to the Old Avestan texts they accompany. Actually, these intercalation ceremonies reflect a ritual that is as old as the version of the long liturgy we know. The journey of the sacrifiants to the hereafter during the recitation of the Old Avestan texts made possible an encounter and an interview with god. The questions and, above all, Ahura Mazdā’s answers are reproduced live in the sacrifice. Thus, all Young Avestan texts belonging to the frašna-genre that is consisting of Zaraθuštra’s questions and Ahura Mazdā’s answers have been composed probably for being intercalated between the Old Avestan texts in the Zoroastrian long liturgy.