(also Zenda Avesta)
The Avesta is the original sacred book of Zoroastrianism. Supposedly written by Zarathushtra himself, the original Avesta was destoryed by Alexander the Great. The current Avesta contains fragments of the original text, and was put back together around the thirteenth century.
The Avesta was written in old Iranian, and contains four main parts. The Yansa - the oldest component contains mostly songs, the Vispred, the Yashts (hymns of praise) and the Videvdat - a collection of purification rituals.