Sifrei Bamidbar 75

(Bamidbar 10:8) "And the sons of Aaron the Cohanim shall blow on the trumpets": What is the intent of this? From (Ibid. 3) "And they shall blow with them," I would think that Israelites, too, may do so; it is, therefore, written "the sons of Aaron." "the Cohanim": whether whole or blemished. These are the words of R. Tarfon. R. Akiva says: whole, not blemished, viz.: It is written here "Cohanim," and, elsewhere, (Vayikra 3:2) "Cohanim." Just as there, whole, not blemished; here, too, whole, not blemished. R. Tarfon: Akiva, how long will you pile up words against us! May I lose my sons if I did not see Shimon, my mother's brother, who was lame in one leg, standing and blowing the trumpets! R. Akiva: Might it be that you saw this on Rosh Hashanah or on Yom Kippur of the Jubilee year? R. Tarfon: I swear that you have not erred! Happy are you Abraham our father, from whose loins Akiva came forth! Tarfon saw and forgot (the day). Akiva expounded of himself and seconded the halachah. Anyone who departs from you departs from his life! (Ibid.) "And they (the trumpets) shall be to you for a statute forever": What is the intent of this? From "Make for yourself two silver trumpets," I would understand that once he made them they would be a heirloom for (all) the generations. It is, therefore, written "to you for a statute forever." They have been given as a statute and not for (all) the generations. From here they said: All the implements that Moses made in the desert were kasher for all of the generations, except the trumpets.