שמות לד,לג : וַיְכַל מֹשֶׁה מִּדַבֵׁר אִּתָם
Moshe’s face was not covered by the veil while speaking to HaShem nor when he spoke to the people, communicating the message of HaShem to them. Although his face sent forth rays of heavenly light, and the people after the sin were not worthy to gaze at this radiance, nonetheless Moshe did not cover his face for the Torah can best be transmitted when the students see the face of their teacher. (The Maharsha in Eiruvim 13b explains that when a student see the subtle expressions on the teacher’s face one can more readily understand him.)
In that Gemara it is related that Rav was a student of Rabbi Meir. In those days students sat in a circle with some sitting in front of the teacher while others sat behind him. Rav is quoted as saying, “I am sharper that others because I studied under Rabbi Meir while I sat behind him. Had I sat in front of him and been privileged to see his face, I would have been sharper.” The Sforno cites this statement to prove his point that Moshe showed his face to the people while instructing them.
