There seems to be a relationship between the words "river" (יאר) and light (אור), that is only underscored by the fact that "river" in Hebrew (נהר) is essentially the same word as "light" in Aramaic (נהרא).
I am looking for a conceptual relationship (preferably, on the level of דרוש) between the two concepts, something that would explain their coming from very related roots in לשון הקדש, as developed in classical Jewish sources (Talmud, Rishonim, Acharonim).
Thank you very much.