"This I ask you, O Ahura, tell me truly: who, by procreation, is the primal father of truth? Who created the course of the sun and stars? Through whom does the moon wax and wane? These very things and others I wish to know, O Mazda." (Yasna 44:1)
Although there is no contemporary recorded evidence of the life of Zarathustra, his teachings were passed down by word of mouth for many centuries. It was not until the Sasanian period (224-651 CE) that they were finally written down in an alphabet especially invented for the purpose. The Avestan language in which they had been composed in all probability had ceased to be understood by all except the priesthood and was otherwise unrecorded. The Avesta included the Gathas, short texts that take the form of inspired utterances, mainly addressed by Zarathustra to Ahura Mazda, expressing what he felt were divinely inspired truths as well as expressions of philosophic enquiry. For example, one of the hymns refers to the contest between good and evil as: "two spirits ... the two thoughts, the two words, the two actions, the better and the evil ...". (Y. 30.3)
The manuscript tradition of the Yasna, the main priestly act of worship in Zoroastrianism, may be divided into two principal categories: the Iranian and the Indian. An important manuscript of this liturgy dating from 1556 CE is the ms. L17, held at the British Library. Avestan manuscripts were often accompanied by translations and commentaries in Pahlavi or Middle Persian (the language of the Sasanians). One of the oldest of all extant Avestan/Pahlavi manuscripts is known as J2 (1323 CE) after its former owner Dastur Jamaspji Minocheherji JamaspAsana. Possibly the oldest Sanskrit version was made on the basis of the Pahlavi version in the late 11th century CE by Neryosangh Dhaval.