TheI-Avesta (evela ku-pahlavi abestāg) iqoqo lemibhalo engcwele yenkolo yamaMazde futhi yakha incwadi engcwele, ikhodi yobupristi yamaZoroaster. Kwesinye isikhathi waziwa eNtshonalanga ngaphansi kwegama eliyiphutha likaZend Avesta. Kubhalwe ezifundeni eziningana ze-Iranian yasendulo, ebizwa ngokuthi yi-avestic. Izingxenye ezindala kakhulu, ezamagatha, ngolimi oludala njengolukaRig Veda (Vedic Sanskrit), "Gathic", ezinye ezisekupheleni kwe-Avestic. Konke kubhalwe ngezinhlamvu zama-Avestic.