Old Church Slavonic or Old Church Slavic was the first literary Slavic language, based on the old Slavic dialect of the Thessaloniki region. The 9th century Byzantine Greek missionaries Saints Cyril and Methodius are credited with standardising the language and using it for translating the Bible and other Ancient Greek ecclesiastical texts as part of the Christianization of the Slavic peoples. It played an important role in the history of the Slavic languages and served as a basis and model for later Church Slavonic traditions, and some Eastern Orthodox and Eastern Catholic churches use Church Slavonic as a liturgical language to this day.