This study aims to analyze and elucidate the phonological features of the “Tabari Translation of Tafsir Kitab-Allah,” authored by Abu al-Fadl ibn Shahrdavir Daylami, an eminent scholar from Northern Iran in the late 8th century AH. The significance of this text lies in its role as a rare, surviving example of religious literature written in the Tabari language, serving as a vital bridge between classical exegetical texts and the local dialects of the Caspian region. From a linguistic perspective, investigating such works is essential for bridging the existing gaps in our understanding of the phonological evolution of Iranian languages during the Middle period.

The research is fundamental (theoretical) in its objective and employs a descriptive-analytical methodology based on content analysis. The corpus of the study includes two volumes of the manuscript of the Tabari translation of the Quran, selected through purposive sampling. In the process of data analysis, a structuralist approach was adopted to extract and classify phonological transformations across various linguistic contexts, including both lexical items and verbal forms.

The analysis of the data extracted from the linguistic corpus reveals that the language utilized in this text possesses distinct phonological characteristics and specialized phonological processes, which reflect the dialectal state of Mazandaran in the 8th century AH. The most prominent of these processes include: the substitution (abdal) of certain consonants, the elision of consonants at the word-final position and within sentential contexts (particularly at the end of certain prepositions and verbal stems), the occurrence of metathesis (displacement of sounds) in several common words, as well as several rare phonological transformations that appeared sporadically throughout the text.

The findings of this investigation indicate that among the various phonological developments in this work, the frequency of “substitution” and “metathesis of consonants” was significantly higher than that of “elision” and other phonological features. This high frequency suggests a linguistic inclination by the author toward standardizing specific phonological patterns to facilitate the transmission of complex exegetical concepts to the native audience. The final results of this research not only contribute to a more precise understanding of contemporary texts of the same era but also serve as a documentary source for the study of the history of Tabari dialect phonology and its evolution in the transition from Middle to New Iranian languages.