I understand that that the Torah tells us that there is a mitzvah to blow a horn on Rosh Hashanah, but why is it specifically a ram’s horn? Is that a mitzvah, or just tradition?
The Talmud tells us that in order for a horn to be valid for Rosh Hashanah blowing, it needs to be a shofar. Well, what is that?
It’s Got to Be Hollow
In the Bible, we find two words that are commonly translated as “horn”: keren (קרן) and shofar (שופר). Keren (the etymological great-uncle of the English words “horn” and “corner”) refers to any animal horn. Shofar, by contrast, refers to a very specific kind of horn.
There are two general types of animal horns. Sheep, goats and others have horns which consist of a sheath of keratin (the stuff that fingernails are made of) covering a bony core. This inner core can be easily removed, and you are then left with the keratin sheath, which forms a naturally hollow structure that can be used to blow musical notes.
Other animals, like the deer or the giraffe, have horns or antlers that are made of solid material. These too can be made into a horn for blowing by drilling a hole through the horn.
The word shofar is linguistically linked with shefoferet, a naturally hollow tube or reed. Thus, it is only the first type of horn that is called a shofar, and solid horns are out.
Cattle Are Out Too
For every rule there is an exception. Although both oxen and cows have horns that can be hollowed, we nevertheless find that the Torah refers to the horns of these animals only as keren and never as shofar. Thus, they are also non-shofars, and may not be blown on Rosh Hashanah.
There is a deeper reason for this as well: There is a Talmudic dictum that “an accuser may not act as defender.” On Rosh Hashanah we are judged for our sins. The mother of all our sins is undoubtedly the golden calf our ancestors worshipped in the desert. Since cows and their horns are associated with the “accusation,” we do not blow their horns as we seek G‑d’s forgiveness on Rosh Hashanah.
But Why the Ram?
After excluding keren-bearing bovines and solid-horned animals, we are still left with a host of kosher animals with hollow horns. So why is the ram king?
The ram’s horn recalls the binding of Isaac, when Abraham was ready to sacrifice his only son, stopping only when an angel showed him a ram whose horns were entangled in the nearby thicket. Thus, the Talmud tells us, when we blow a ram’s horn, it is as if we are reenacting this amazing act of devotion.
Also, the bent shape of rams’ horns (and those similar to them) are emblematic of our contrite state, as we humbly approach G‑d and ask Him to grant us a good new year.
How About the Kudu?
There are some Yemenite communities that favor the very large horn of a greater kudu (a woodland antelope). The origins of this custom remain unclear. So unless this is your custom, it is preferable to stick to the ram’s horn.
In fact, some rabbis (notably Maimonides) rule that only a ram’s horn may be used. The halachah does not follow this opinion, so if there are no rams’ horns you can use a horn from a different animal, but all agree that a ram’s horn is ideal.
The Great Shofar
Our sages tells us that on the entire day Abraham bound Isaac, he saw the ram tearing himself free from one thicket and becoming entangled in another. G‑d told Abraham: “Thus are your children destined to be caught in iniquities and entangled in misfortunes.”
Abraham then turned to G‑d and asked, “Master of the World! Will it be like this forever?”
G‑d replied, “In the end, they will be redeemed by the horns of this very ram, as the verse states, ‘G‑d will blow with the shofar and go forth in southern tempests.’” May this be speedily in our days!