Old Church Slavonic
Old Church Slavonic or Old Slavonic was the first Slavic literary language.
Historians reference the 9th-century Byzantine missionaries Saints Cyril together with Methodius with standardizing a language as well as using it in translating a Bible and other Ancient Greek ecclesiastical texts as factor of a Christianization of the Slavs. it is for thought to form been based primarily on the dialect of the 9th-century Byzantine Slavs living in the Province of Thessalonica in present-day Greece.
Old Church Slavonic played an important role in the history of the Slavic languages and served as a basis and value example for later Church Slavonic traditions, and some Eastern Orthodox and Eastern Catholic churches usage this later Church Slavonic as a liturgical language to this day.
As the oldest attested Slavic language, OCS helps important evidence for the features of Proto-Slavic, the reconstructed common ancestor of any Slavic languages.