“Then when they are fifty years old they shall retire from the work force and not serve any more.” (BeMidbar 8:25)
The members of Shevet Leyve – the Leveyim – were assigned to assist the Kohanim. They had various responsibilities. These included singing in the Mishcan and guarding it from all ritual impurity. Our pasuk indicates that the Leveyim were required to retire from their responsibilities upon reaching the age of fifty.
What responsibilities could the Leyve no longer perform when reaching the age of fifty? In order to answer this question, we must be aware of an important detail in the transport of the Mishcan. How was the Mishcan transported? Most of the Mishcan was transported by wagon. However, the most sacred components were carried directly by the Leveyim – specifically, by the member of the family of Kahat. These components included the altars, the Shulchan, Menorah, and the Aron.
Rashi explains that a Leyve reaching the age of fifty was only disqualified from direct carrying. He could not participate in the transport of the Aron and those components that were carried directly by the Leveyim. His age implied declining strength. This rendered him unfit for this physically challenging task. However, he still participated in other tasks performed by the Leveyim. He sang in the Mishcan, opened and closed the entrances, and assisted in loading the wagons used to transport other portions of the Mishcan.
Nachmanides differs with Rashi. He maintains that, upon reaching the age of fifty, the Leyve was also disqualified from participating in the songs of the Mishcan. Nachmanides, in his commentary on Maimonides’ Sefer HaMitzvot, offers an interesting explanation for his position. He explains that, once the Leyve reached the age of fifty, he was no longer fit to carry heavy burdens. In order to avoid confusion, he was also disqualified from participating in song. Participation in song would create the impression that the elder Leyve was fit for all service – even carrying portions of the Mishcan. In other words, age rendered the Leyve fundamentally unfit for carrying heavy burdens. His disqualification from participating in the song of the Temple was the result of a secondary consideration. He was restricted from song in order to avoid confusion.
The Torah is composed of 613 – Taryag – mitzvot. Should this restriction upon the Leyve be included within the 613 mitzvot? The answer depends on the criteria for including a command among Taryag. Taryag is a permanent system. It applies in all generations. Therefore, one of the criteria for inclusion in Taryag is that the commandment must not be fixed to a particular historical moment or circumstance. For example, Hashem gave Bnai Yisrael various commandments in preparation for Revelation on Sinai. One of these was that the people could not approach or ascend the mountain. These instructions only applied during the period of Revelation. These restrictions cannot be counted as elements of Taryag. Therefore, in order to answer our question regarding this restriction on the Leyve, we must ask another question. Does this restriction apply in all generations, or was this restriction only relevant during the sojourn in the wilderness?
Halachot Gedolot includes the restriction upon the Leyve’s service among the Taryag Mitzvot. Apparently, he maintains that this restriction applies in all generations. Maimonides objects. He argues that this restriction only applied during a specific historical period. Therefore, it is not appropriate to include this restriction within Taryag.
Nachmanides supports the opinion of Halachot Gedolot. However, before we consider Nachmanides’ argument, we must consider two related issues.
First, as we have explained, during the sojourn in the wilderness, the Mishcan was transported on a regular basis. Once Bnai Yisrael entered the land of Israel, this changed. At first, the Mishcan was placed at a permanent location. Later, the Bait HaMikdash in Yerushalayim replaced the Mishcan. In other words, the Mishcan was no longer regularly transported in its entirety, or even partially. However, the Aron was moved on a few occasions. One of these occasions was the transfer of the Aron to Yerushalayim. King David arranged for this operation.
Maimonides acknowledges that there is a mitzvah that regulates the transport of the Aron. This mitzvah is included in Taryag. It stipulates that the Aron must be carried directly. It cannot be transported by wagon or some other conveyance.
Second, in the wilderness, the Leveyim were responsible for the transport of the Aron. However, according to Maimonides, this is no longer the case. The Kohanim are now responsible for this task. No other member of Shevet Leyve can perform this task. Maimonides explains that during the period of the sojourn in the wilderness, there were few Kohanim. It was not feasible to charge this small group with this responsibility. Therefore, the task of transporting the Aron was assigned to the Leveyim. However, when the number of Kohanim increased, this task was permanently assigned to the Kohanim.
We can now understand Nachmanides’ objection to Maimonides’ position. Maimonides maintains that the restriction upon the Leveyim’s service beyond the age of fifty is not one of the Taryag Mitzvot. Nachmanides raises an obvious objection. The restriction upon the Leyve who reaches the age of fifty against carrying the Mishcan was a commandment during the sojourn in the wilderness. It was, essentially, a parameter. It defined who was fit and who was disqualified from performing this task. This restriction dictated that one over the age of fifty was not permitted to directly carry any component of the Mishcan – including the Aron. The task of carrying one component of the Mishcan, the Aron, is a mitzvah counted among Taryag. It is reasonable that the parameter of who is qualified and who is disqualified from performance of this task should remain in force. True, the restriction should now apply to the Kohanim and not the Leveyim. Nonetheless, the restriction should continue to be regarded as a mitzvah that defines a fundamental parameter regarding the transport of the Mishcan. It should also be noted that Maimonides does not only refuse to count this parameter as a mitzvah. He does not even regard this parameter as in force. It simply no longer applies!
How can we explain this dispute between Maimonides and Nachmanides? It seems that Maimonides and Nachmanides argue over the fundamental nature of the restriction upon the Leyve. There are two ways to understand this restriction. One approach is that this restriction is a law governing the transport of the Aron or Mishcan. The transport of the Aron requires physical strength. The job demands a robust person. A person who is over the age of fifty is simply not assumed capable of performing this duty. In other words, this is not a law directly governing the functions of the Leyve. It is a law regarding the transport of the Mishcan. The second approach is that the Leveyim were assigned a number of tasks. One of the most important was the transport of the Mishcan or Aron. If a person could no longer fulfill this difficult task, he was disqualified from serving as a Leyve. In other words, this law governs the qualifications for serving as a Leyve.
Nachmanides maintains that this law is merely a restriction in who can carry the Aron. Therefore, as long as there is a mitzvah to transport the Aron, this restriction continues to function. It deserves to be counted among Taryag.
Maimonides disagrees. He maintains that the restriction placed upon the Leyve in the wilderness was far more than a parameter defining whom could carry the Mishcan and Aron. The law in the wilderness defined who was included and counted among the Leveyim, and who was not completely included. The responsibility for transporting the Aron and Mishcan was a fundamental aspect of the Leyve’s job. A Leyve that could no longer perform this task could not be completely counted as a Leyve.
We can now respond to Nachmanides’ objection to Maimonides’ position. The age restriction that applied to the Leyve was only reasonable because the task of transporting the Mishcan was a fundamental aspect of his job. He could not perform this task. Therefore, he could not be completely counted among his brethren. Maimonides maintains that this responsibility was transferred to the Kohanim. Therefore, it is no longer part of the Leyve’s job description. It follows that the inability of the Leyve to perform this task should no longer disqualify the Leyve. This task is no longer his responsibility. His fitness can no longer be evaluated on the basis of his ability to carry heavy burdens.
The responsibility for carrying the Aron has been transferred to the Kohen. However, this is a very minor aspect of the Kohen’s role. It is not reasonable to disqualify a Kohen from being counted among his brethren because he cannot perform this task. The task is not fundamental to the role of Kohen.
In short, according to Maimonides, a law that disqualifies a Leyve of Kohen on the basis of advanced age is no longer feasible. It presumes that the person’s primary role is impacted by age. This is no longer the case with the Leyve. He has been relieved of his responsibility to carry the Mishcan or Aron. This is also not the case with the Kohen. Albeit that he is responsible for transporting the Aron, this is a minor aspect of his job.
 Rabbaynu Shlomo ben Yitzchak (Rashi), Commentary on Sefer BeMidbar 8:25.  Rabbaynu Moshe ben Nachman (Ramban / Nachmanides), Commentary on Sefer BeMidbar 8:25.  Rabbaynu Moshe ben Nachman (Ramban / Nachmanides), Critique on Maimonides’ Sefer HaMitzvot, Third Principle.  Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Sefer HaMitzvot, Third Principle.  Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Sefer HaMitzvot, Third Principle.  Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Sefer HaMitzvot, Mitzvat Aseh 34.  Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Sefer HaMitzvot, Mitzvat Aseh 34.  Rabbaynu Moshe ben Nachman (Ramban / Nachmanides), Critique on Maimonides’ Sefer HaMitzvot, Third Principle.