In the Moreh Nevuchim the Rambam explains the requirement that the Kohen be unblemished to be based upon public opinion. Unfortunately, people do not tend to judge an individual by his own true value, but rather by the external perfection of his limbs and the beauty of his garb. It was, therefore, necessary for the Kohanim to be unblemished to ensure that the Bais Hamikdash would be universally respected.
The Rambam notes that this requirement only applied to Kohanim, who offered sacrifices and were the people’s agents in entreating Hashem for forgiveness. The Leviim, however, whose sole function was to perform the vocal music, were disqualified from service only upon losing their voice. Horav Eliyahu Munk Z”l cites the Rekanti who observes that while physical defects did not render the Levi unfit for service, he was subject to an age limit of fifty. This contrasts with the Kohen who had no age limit for service. The Rekanti explains that the Levi, who performed a physical function, served as long as he possessed his vitality and inner zeal. The age of fifty was arbitrarily chosen as the time at which his strength began to wane. The Kohen, however, was a spiritual mentor, a teacher of the people, who grew wiser with age as he gained life experience. This is a remarkable statement which carries a timeless messsage.
