After Matan Torah the Posuk says that after the Shofar blast it is permitted to climb the mountain. Rashi says that Matan Torah ended with a Shofar sound. Rashi says that this Shofar was taken from the animal brought after the akeida.
The Ramban on that Posuk quotes Rashi and he asks that Avraham Avinu took that Ayil and he offered it as a Korban. The Halacha is as the Ramban brings from Maseches Zevachim (85b) that when you burn a Korban Olah it is Kulo Kalil, it is entirely burnt including the horns (the Shofaros). How can that possibly have been the Shofar at Har Sinai? The Ramban says that perhaps HKB”H took the ashes of that Shofar and recreated it so that it should be back into a Shofar.
The Teshuvos Dovev Mei’sharim of the Tchebiner Rov (Rabbi Dov Berish Weidenfeld (1881 - 1965)) asks on the Ramban that there is a Mishna that says if you glue together a Shofar’s pieces it is Pasul. For those who want to see it inside the Dovev Mei’sharim is in Cheilek Daled, Teshuva Ayin Hei.
