The Council of Tours in 1163, under Pope Alexander III, issued a decree requiring priests to preach in the vernacular languages of their congregations rather than solely in Latin. This decision acknowledged the linguistic reality that most laypeople could not understand Latin and sought to make religious instruction more accessible to ordinary Christians.

This mandate stimulated the development of vernacular religious literature, including sermons, devotional texts, and biblical paraphrases in Old French, Occitan, German, and other European languages. It encouraged clergy to develop literary skills in vernacular tongues, contributing to the standardization and prestige of these languages. The resulting body of vernacular religious poetry and prose laid groundwork for later secular vernacular literature by demonstrating that complex theological ideas could be expressed in local languages.