Social classes in Ancient Persia

Persian society was modeled on a quadripartite scheme based on the Avesta, the sacred scriptures of the Zoroastrians.
The categories were:  priests, warriors, farmers and artisans.
The first three were each under the protection of one of the Empire’s three great sacred fires.

Azar-Faranbagh for priests, Azar-Gushnasp for the King of Kings and warriors and Azar-barzin-Mihr for farmers.
Society in the Sassanid era was hierarchical. The word caste has been applied to designate its classes. Membership in a category was hereditary and the barriers to a higher level were, in principle, impenetrable.