Comentário sobre Números 4:19

ושמו איש איש על עבודתו ואל משאו, assign to each of them his specific duty in order to avoid a free for all. By doing this, you will insure that each Levite will wait patiently until his turn comes to carry out his assigned duty.

וזאת עשו להם, "and this is what you are to do for them, etc." This means that the Kehatites were not to consider themselves as performing their task on their own authority. If they would do so there was a danger that anyone who loved the sacred vessels would arrogate to themselves a part in the service of the Tabernacle. Rather, all the Kehatites did was to be under the supervision of Aaron and his sons and at their direction. This would ensure that every member of the Kehatites knew his place. This is the deeper meaning of the words אותם איש. When the Torah continues ולא יבואו לראות, "so that they will not come and take a (unauthorised) look at the Sanctuary when the vessels are being covered," this tells us that even looking at something that was not their place to see could prove deadly. The words ושמו אותם stress that it was not enough for each Kehatite to know his place but that they had to wait before putting their hands on the vessels they were to carry until instructed to do so by Aaron. This was different from what the clan of Gershon did; although in that connection the Torah also writes that their task was performed על פי אהרון, at the command of Aaron, the Torah did not add the cautionary words ושמו אותם as they did not face death if they acted prematurely (compare 4,27).

וחיו ולא ימותו, "so that they may live and not die, etc." The Torah means that carrying the Holy Ark whose contents, the Torah (and the Tablets), is a dispenser of life will ensure that the Kehatites carrying same would enjoy long life. Seeing that some Kehatites might be afraid that unauthorised touching or viewing would cause them to die, the Torah adds the words ולא ימותו, "so that they will not die," to put at rest such fears of the Kehatites that they would die by accidentally touching or viewing what they were not supposed to view or touch.