Shaykhul Islaam Ahmad ibn Taymiyyah 728AH (May Allah have mercy on him) said,

اللسان العربي شعار الاسلام و أهله, و اللغات من أعظم شعائر الأمم التي بها يتميزون

“The Arabic tongue is the symbol of Islaam and its people, and languages are of the most significant signs by which nations are distinguished.”

Source: Sharh Iqtidaa as-Siraat al-Mustaqeem pg.340 [Official print from the Mu’assasah ash-Shaykh Muhammad bin Saalih al-‘Uthaymeen al-Khayriyyah]