I thought Gezeirah Shavah requires Mesorah

Question

In Masecheth Rosh Hashanah (9b), the Gemara uses a Gezeirah Shavah from Tishrei, with the word שנה, to support the Mishnah's ruling that 'Orlah is counted from Tishrei. In response, however, the Gemara challenges that Nisan has the same word and, therefore, the Gezeirah Shavah could be applied to Nisan, a point which is subsequently rejected based on a logical argument.

Wait a second! I thought that a Gezeirah Shavah can only be established by a tradition from one's teacher! While I understand the logical argument on both sides of this particular debate, of what relevance is either argument? Either there's a tradition, or there isn't. So what's going on here?!

Answer 1

There are two different types of gzeirah shava

1. specific words were part of the mesorah but the pesukim used and / or the actual item that was derived from the gzeirah shava may not have been part of the mesorah.
2. The content of the limud was part of the mesorah but not the words used in the gzeirah shava.

Halichos Olam Shaar 4. See also Ramban sefer hamitzvos 2

See here where they explain that Rashi and Ramban maintain that one may associate a halacha from a gezeirah shavah only if he received the halacha that is "being derived" from his teacher. The actual words of the gezeirah shava may not have been transmitted by his rebbi.

"אין אדם דן גזרה שווה מעצמו" (פסחים סו.). רש"י: "אלא אם כן למדו מרבו". רק אם החכם קיבל את ההלכה מרבו, רשאי הוא לדרוש לה "גזרה שווה", ולעשות את הפסוק אסמכתא להלכה שבידו. אך אין לחדש הלכה באמצעות גזרה שווה. בלשון הירושלמי: "אדם דן גזרה שווה לקיים תלמודו" (ירושלמי, פסחים ו:א). טעם לכך, כתב רמב"ן בספר המצוות, כי ישנן מלים רבות הכפולות בתורה, ואם ידרוש אדם מעצמו, פעמים ידין רוחו, ויהרוס כמה דינים, ויסתור כמה עניינים.

However, this seems to be an oversimplification in the definition of a gzeirah shava. None of the Rishonim cited nor the Yerushalmi is a proof for this: the Yerushalmi is simply saying that for a known halacha one may find a hint for his halacha using a gzeirah shava...i.e. using a memory device similar to an actual gzeirah shava but by no means is this an actual drasha from a gzeirah shava.

See Encyclopedia Talmudit גזירה שוה entry where this and more detail can be found.

Answer 2

I once asked a rebbi of mine this very question, in a different context. The Gemara in Kiddushin 14b discusses a Gezerah Shavah using the word שכיר, a word that is found a number of times in the sections of the Torah that deal with slaves/servants. Tosofos there, s. v. מוכר, takes the liberty of applying this Gezerah Shavah to other instances of the word in the Torah.
I asked my rebbi, how can Tosofos create a Gezerah Shavah without a direct tradition. He answered that a direct tradition is only required to identify which words are used in a Gezerah Shavah. However, once it is known that a certain word, such as שכיר, is meant to be used, the rules of Gezerah Shavah can and should be applied to any instance in the Torah where the word is mentioned. Of course, only someone of great Torah stature can know how to apply each GSh, and we would not attempt to do so nowadays. But Amoraim and even Rishonim can do so.
As an interesting addition, the assumption the one cannot make a GSh without a tradition is one stated by Rashi and others in many places across Shas. Interestingly enough, the sefer Kin'as Sofrim, a commentary on the Sefer Hamitzvos of the Rambam (in Shoresh 2), maintains at length that the Rambam disagrees with Rashi on this account, and holds that later Sages of the Sanhedrin could develop a Gezerah Shavah on their own, using some unknown principles. Even if his thesis is correct, it nevertheless seems to be a lone opinion.