How did Middle Persian remain important to Zoroastrians after the Sasanian period?

Following the fall of the Sasanian Empire and the rise of Islam, Middle Persian—also known as Pahlavi—remained vital to Zoroastrians as the primary language for preserving their religious and cultural heritage.12

During the 9th century, a period of Zoroastrian renascence under Islamic rule, scholars produced significant Pahlavi texts to safeguard the essentials of their faith from potential loss. Key contributions included:32

• The Dēnkart: An encyclopedic "Acts of the Religion" that provided a summary of the 21 books (nasks) of the Avesta, most of which had been lost.2
• Religious and Philosophical Works: Texts such as the Bundahishn (a cosmology), the Mēnōk-i Khrat (a summary of doctrine), and the Book of Artāy Virāf (describing the afterlife) were composed to codify Zoroastrian beliefs.2
• Apologetic Literature: Authors like Mardān-Farrukh wrote works such as the Shkand-Gumānik Vichār to defend the Mazdean religion against competing faiths, including Manichaeism, Christianity, Judaism, and Islam.2

By maintaining these texts, Zoroastrians ensured that their sacred traditions and historical identity survived as a minority community in Iran.13