Comentario citado sobre Isaías 35:2

ולבני לוי, “to the sons of Levi, etc.” Seeing that in connection with the priests the Torah had spoken of “Pinchas and his descendants after him,” (Numbers 25,13), i.e. that the priesthood would be hereditary in character, the Torah had to teach us that the same principle applied to the duties and privileges associated with the Levites. The Torah chose the word: “sons of” seeing that it had not previously used the word “after him” as it had in connection with the priesthood bestowed on Pinchas. The letter ו in ולבני, is an additive, adding something to the original i.e. the subject discussed previously, the priesthood. Just as the term “an eternal salt-like covenant” applies to the priests and the priesthood, so the same term applies to the Levites and their duties and privileges.
These portions which we conclude here describe that after the various challenges to the already prevailing hierarchy had been disposed of, the staff of Aaron had to sprout not only as symbol of his personal status but as symbol once and for all that the functions of both the Levites and the Priests had been ordained from on high not just for this generation but on an ongoing hereditary basis. As mentioned previously, the sprouting of Aaron’s staff contained not only the message of Aaron’s “superiority,” but the whole phenomenon was to serve as warning to any future challengers of the system that G’d’s punishment would be swift, just as the almond tree develops swiftly. We find strong allusions to this concept in Psalms 92,8, in Isaiah 35,2, in Hoseah 14,6 and in Proverbs 11,28. In all of the verses mentioned the verb פרח does not only describe development, growth as such, but swift development.

והנה פרח מטה אהרן, “and behold the rod of Aaron of the house of Levi, had begun to sprout blooms.” From this verse we learn that there are two kinds of flowers, פרח and ציץ. Not only did these blooms sprout forth, but they retained their freshness and did not wilt, as do normal flowers. The flowers were still in bloom after having already produced fruit, i.e. almonds. We have proof of the above from the Talmud, tractate Yuma folio 21, (based on Isaiah 35,2) as well as from the chapter in the Talmud discussing items in the Temple that were hidden to prevent them from falling into the hands of our enemies. Some sages believe that this staff of Aaron was hidden during that period, which would prove that it and its fruit had remained in prime condition for hundreds of years.