Rashi explains Moshe’s critique in the following manner: “You decided the matter to your benefit without considering that you were being disrespectful. You should have responded to the suggestion about instituting sub-leadership by saying, ‘Our teacher Moshe, from whom is it more appropriate to learn: you or your student? Is it not better to learn from you because you suffered over the Torah?’” The last few words, “because you suffered over the Torah,” seem to be superfluous. It would have been sufficient merely to posit that it is better to learn from the master than to learn from the student. Why does Rashi add the fact that Moshe toiled and suffered over the Torah?
Horav Moshe Feinstein, z.l., explains that as far as the student is concerned it is quite possible, at times, that the “student” teacher can have a greater success rate – or be more effective in reaching the student than the “master” rebbe/teacher. Rashi is, however, teaching us a very significant lesson in education by defining the essence of a rebbe, Torah teacher, and, by extension, indicating from whom we should learn. A true rav/rebbe is one who toils and suffers over the Torah that he will later expound to perfection, exactly as Hashem transmitted it. He does not rely on his own acumen. Regardless of his brilliance, he labors to the point of suffering, leaving no stone unturned in his quest to understand the Torah fully. This is the type of teacher from whom we should learn Torah. Scholarship does not mean everything – it is how one achieves that level of scholarship which determines if he is an appropriate person to transmit Torah to others.