Towards the end of the Parsha, there is the account of Moshe Rabbeinu ‘s request that Hashem appoint an able successor to lead the Jewish people into Eretz Yisrael. Hashem answered him that his faithful student, Yehoshua, is the appropriate choice. Chazal elaborate on the dialogue that took place between Hashem and Moshe. They tell us that Moshe asked that his own sons succeed him as leader, however Hashem refused this request, because “your sons sat and were not osek beTorah” , whereas, Yehoshua was the rightful successor because “he would come early to, and leave late from, your beis medrash, and would arrange the benches and cover the tables.” There are two difficulties with this Medrash; Firstly, if Moshe’s sons were not osek b’Torah then how could Moshe Rabbeinu have had any expectation that they could lead the Jewish people? Secondly, it would seem that Hashem was comparing Moshe’s sons to Yehoshua in the same area of hanhago - that of being osek b’Torah. However, when Hashem praised Yehoshua he stressed the fact that he set up the Beis Medrash - this does not seem to have any relevance to being osek beTorah. What exactly was the nature of the comparison of Moshe’s sons to Yehoshua?
Rav Yosef Shalom Elyashiv Shlita explains that Moshe’s sons were talmidei chachamim and they were learned enough to lead the Jewish people - that is why Moshe believed that they were fitting candidates for succeeding him. However, Hashem replied that this was not sufficient; when He said that they “sat and were not ’osek b’Torah’” He meant that they sat and learned for themselves and were not osek with others in Torah. In contrast to their lack of being involved in helping other people’s Torah, Yehoshua would set up the Beis Medrash and thereby enable others to learn Torah - that is considered being ‘osek b’Torah’.
There are a number of important lessons that can be derived from Rav Elyashiv’s explanation, however, there seems to be one specific difficulty with it - it would have seemed that being osek b’Torah only implies learning Torah for oneself, where is the allusion to enabling others to learn Torah?
In order to answer this it is necessary to understand the basic definition to the mitzva of Talmud Torah. The Rambam writes that there are two sources for the mitzva; “You shall teach them to your children” and “you shall teach them sharply to your children.”. From these commands to teach children the Rambam derives that a person must learn Torah - the fundamental reason given for learning Torah is so that one can teach it to his children. We see from here that the mitzva of ‘Talmud Torah’ refers to teaching as much as to learning. Moreover, the Rambam brings the Chazal that ‘children’ also refers to students, and that a fundamental part of the mitzva is to teach people even if they are not one’s own children. Thus, it is quite understandable that Rav Elyashiv can translate, being ‘osek b’Torah’ as meaning ‘causing others to learn’ Torah.
Another source for the concept that ’Torah’ intrinsically involves enabling others to learn Torah is found in the Gemara in Avoda Zara. The Gemara says that world history is split into three periods of two thousand years: The first is called the ‘two thousand years of nothingness’, The second period is known as the ‘two thousand years of Torah.’ The commentaries explain that the years of nothingness are so called because of the lack of Torah in the world during that time, whereas the years of Torah mark the beginning of Torah’s presence in the world. The Gemara says that the years of Torah began with time that Avraham began teaching Torah to the world, as represented by the ‘souls that they made in Charan’. However, there is a difficulty with saying that the years of Torah began only at this point in time. There are many maamarei Chazal which clearly state that there were great people who lived before Avraham and learned Torah, and yet they lived in a time that is described as being absent of Torah, moreover Avraham Avinu himself learnt Torah long before he began teaching others - the era of ‘Torah’ only began with the ‘souls that they made in Charan’. - why is this the case? Rav Zev Leff Shlita explains that Avraham Avinu did something more than his illustrious predecessors - he taught Torah. The era of ’Torah” only begins when Torah is taught as well as learnt.
The Maharsha makes a comment that develops this theme further by showing that, in addition to regular ’learning’ of Torah even the concept of ‘Ameilus b’Torah’ is intrinsically bound up with teaching Torah. The Gemara derives the importance of ‘ameilus b’Torah’ from various passukim in Tanach that mention the word, “l’amal’’ (to toil). The Maharsha writes that the letters of ‘l’amal’ (lamed, ayin, mem and lamed) make an acronym of ‘lilmod al menas lelamed.’
We have seen many sources that show that learning and teaching Torah are in the same category. It still needs to be explained why teaching Torah is so fundamental in Jewish thought. The Ben Ish Chai zt’l provides us with a deeper understanding of this inyan. He brings the Gemara in Sanhedrin that quotes the passuk in Shelach saying that person who serves other gods has “degraded the word of Hashem.” The Gemara then describes other modes of behavior that deserve this devastating indictment. Surprisingly, the Gemara adds that the passuk includes “one who learns and does not teach.” The Ben Ish Chai asks why the Gemara speaks so harshly about one who learns but does not teach. He explains that the Torah is eternal and it’s eternal nature is preserved by passing on its teachings to the next generation. However, he writes that “a person who learns but does not burden himself to teach his fellow damages the eternal nature of the Torah because the Torah that he learns cannot move on to the next generation…therefore it is understood why Chazal describe this man in such a severe manner - because he prevents the chain of the passing down of Torah from generation to generation and nullifies the Torah’s eternal quality..”
This also helps us understand why it was important that the leader of the Jewish people be one who causes others to learn Torah - his role was to preserve and continue the mesora and thereby preserve the eternal nature of the Torah.
We have seen how intrinsic teaching Torah is to the mitzva of learning Torah. Moroever, whilst teaching Torah is a great chesed to other people, it is also clear that there is a very significant element of bein adam le’utsmo in teaching Torah - it helps develop our appreciation of the eternal nature of Torah and to play a role in passing it on to the next generation.
 Bamidbar Rabbah, 21:14.
 This question is asked by Rav Yosef Shalom Elyashiv Shlita, Divrei Aggada, p.319.
 See his continuation in Divrei Aggada, p.319-20 where he elaborates on the necessity to share one’s Torah with those who are distant from the true path. We also learn from his explanation that the ability and willingness to share Torah with others is a key trait in determining an effective leader.
 The Mishna in Avos, 1:1 tells us that we must “establish many students.” The Tiferes Yisroel writes that it is not enough to merely teach one’s own children but one must teach other Jews as well.
 Avoda Zara, 9a.
 Chazal say that Adam HaRishon, Noach and Shem v’Ever learnt Torah.
 ‘They’ refers to Avraham and Sarah.
 Avraham was 52 years old when the era of Torah began - see Rashi, Avoda Zara, 9a.
 One may ask that Avraham was not the first to teach Torah - Shem and Ever had yeshivas where they taught students. The difference is that Avraham taught Torah to those who did not otherwise have any desire to learn it, whereas Shem and Ever waited for people willing to learn to come to them - see Rambam, Hilchos Avoda Zara, Ch.1 Halacha 3, with Raavad and Kesef Misha who elaborates on the qualitative difference between Avraham‘s teaching and that of Shem and Ever. Also see Shut Chasam Sofer, hakdamo to Yoreh Deah, and Chomas Hadas of the Chofetz Chaim who elaborate on the differences between Avraham and the great men that preceded him. Another possible difference between Avraham and Shem and Ever is that taught already righteous people, whereas Avraham drastically changed the direction of people’s lives - this is supported by the Gemara’s citing of the passuk that refers to the souls that Avraham made - this suggests that merely teaching a person Torah is not the end goal, rather this is a means to making people change their lives through the torah that they are taught. Rav Yaakov Emden zt”l writes that when the Mishna in Avos ( 4:6) says that the highest level is ‘lilmod al menas laasos‘, it means learning in order to make others do - this is considered a higher level than lilmod al menas lelamed because the goal of teaching is to cause greater Mitzva observance.
 Sandedrin, 99b.
 See Iyov, 5:7. Mishlei, Ch.16.
 Maharsha, Sanhedrin, 99b.
 Sanhedrin, 99a.
 Shelach, 15:31.
 Included in this list are one who is megaleh panim b’Torah and one who claims that the Torah is not from heaven.
 Benyahu, Sanhedrin, 99a, quoted in ‘Peninei Ben Ish Chai, Shelach, p212.