It is not always easy to engage in the study of Torah and completely understand its content. It is incumbent on the rabbi teaching his student to explain matters again and again, as often as necessary. Despite the difficulties inherent to studying and teaching, the cross-pollination that results from the exchanges between great Sages and their young students is one of the ways in which they glorify the Torah.

Matters of Torah are likened to silk garments: Just as you do not purchase silk garments quickly but you can tear them quickly, so too, matters of Torah are difficult to acquire but easy to lose. By contrast, inconsequential matters can be compared to sackcloth garments: Just as with regard to sackcloth garments, you purchase them quickly but you do not tear them quickly, so too, inconsequential matters are easy to acquire and difficult to lose.

Rabbi Perida had a certain student whom he would teach four hundred times, and ultimately he would learn the material. One day, some people sought Rabbi Perida’s presence for a matter of a mitzva after the lesson. Rabbi Perida taught his student four hundred times as usual, but the student did not learn the material successfully. Rabbi Perida said to him: What is different today that you are unable to grasp the lesson? The student said to him: From the moment they said to the master that there is a matter of a mitzva for which he is needed, my mind was distracted from the lesson. Each moment I said: Now the master will stand; now the master will stand.

Rabbi Perida said to him: Pay attention this time and I will teach you again, as you now know that I will not leave until you have mastered the lesson. He again taught him another four hundred times. A divine voice emerged and said to Rabbi Perida: Would you prefer that they add four hundred years to your life, or that you and your generation will merit the World to Come? He said: I prefer that I and my generation merit the World to Come. The Holy One, blessed be He, said to the angels: Give him this reward and that one.

Rav Nahman bar Yitzhak said: Why are Torah matters likened to a tree, as it is stated: “It is a tree of life for those who hold on to it” (Proverbs 3:18)? It serves to tell you that just as a small piece of wood kindles a large piece, so too, young Torah scholars sharpen the great Torah scholars. This is what Rabbi Hanina said: I have learned much from my teachers and even more from my friends, but from my students I have learned more than from all of them. (Avot deRabbi Natan, version B, chap. 31; Eiruvin 54b; Ta'anit 7a)