In the first episode of the Lashon HaKodesh series, I will be examining the introducion to the Sefer Ha-Egron of Sa'adyah Gaon (b. 882) where we find the first discussion on the nature of Lashon HaKodesh by a medieval Rabbinic Jewish thinker.

References: 

Allony, N. [Ed.] (1969). Ha-Egron. The Academy of the Hebrew Language.

Brody, R. (1998). The geonim of Babylonia and the shaping of medieval Jewish culture. Yale University Press. pp. 317-318; idem. (2013). Sa'adyah Gaon. Liverpool University Press. pp.79-84 [translation of Egron from these pages]. 

Glinert, L. (2017). The story of Hebrew. In The Story of Hebrew. Princeton University Press. pp. 81-85. 

Septimus, B. (1994). Maimonides on Language. in Aviva Doron, ed., The Culture of Spanish Jewry: Proceedings of the First International Congress. Tel Aviv: Levinsky College of Education. pp. 38-39.