Avesta: the collection of sacred texts of Ahuramazdism, the Iranian religion founded by the Bactrian prophet Zarathustra. The Avesta (or Zend-Avesta) contains several kinds of texts: The final redaction of the Avesta took place in the fifth and seventh centuries AD. The Yasna, however, contains a collection of older texts, the Gâthâ's (songs). On linguistic grounds, these texts can be dated in the first half of the firsdt millennium BC; probably, they are even older. They may be composed by Zarathustra;