Original Magic: The Rituals and Initiations of the Persian Magi - Stephen E. Flowers Ph.D. 2017

Words
The History of Iranian Magic

The rituals are accompanied by spoken or sung words, which are fixed and thought to come from the gods themselves or be divinely inspired. These words are learned by heart and passed on verbatim from master to student. The Sanskrit Rig Veda in India represents just such a text: it was composed orally between 1800 and 1400 BCE and passed on verbatim, from mouth to ear, from that time forward. The language of the Rig Veda dates from approximately the same period as the Zarathustran Gathas.

Zarathustra was a professional priest of this cult who was responsible for remembering and performing such chants in the practice of the cult before he had his enlightenment.

The verbal formulas are preserved in their fixed forms, because they had, over time, proved themselves to be effective—they worked in a practical way. When spoken or sung correctly, they had the desired effect. For this reason alone they were memorized and passed on in a fixed form over centuries and even millennia. For the most part these songs alluded to, but did not explain or narrate, the myths already well known to the priests.