Rav Herschel Schachter
Mesorah and Change
The medrash points out that the bracha which Avraham granted his son Yitzchak revolved around the verb, "natan" ("Vayiten Avraham et kol asher lo leYitzchak"). Therefore, years later when Yitzchak formulated his bracha for his son Yaakov, he opened with the words, "Vayiten lecha Elokim." And because Yitzchak's bracha ended with the use of the verb "karah" ("Vayikra Yitzchak el Yaakov"), years later, when Yaakov was formulating his bracha for his children, he started with the same expression, "Vayikra Yaakov el banav." Yaakov concluded his brachot with the expression "vezot asher diber lahem avihem." Therefore, many years later when Moshe Rabbeinu formulated his brachot to Klal Yisrael he too used the same expression, and started with the phrase, "Vezot habrcha." And again, because Moshe concluded his brachot with the expression, "ashrecha yisroel," years later, when King David composed the Sefer Tehillim, he began with the same expression, "Ashrei haish."
The medrash learns from the pasuk, "mezekeinim etbonan" (Tehillim 119), that each generation learns from and emulates the practices of the earlier generation. The rabbis of the medrash understood quite well that it would be unreasonable to expect all the generations to always use the exact same expressions. Times change, attitudes change, and expressions of speech change. The rabbis just felt that the practices of each generation should be connected with those of the earlier generations.
If the Rabbis felt this way with respect to formulating brachot certainly they would feel more so with respect to halachot of how to keep the mitzvot. True, the Torah scholars of each generation - if they are qualified- may express an opposing view to those of earlier generations. We see many times in the Mishnayot that a later Beit Din overturned the psak of an earlier Beit Din. But there still must be a "hemshech" and a connection to the Torah views of the earlier generations. To use the terminology of the Rav, "chiddush" (new insight) is acceptable, but "shinui" (change) is not; and one must have a very strong mesorah to know how to distinguish between the two. Mattan Torah did not occur yesterday. Our Torah of today is only valid to the extent that it has been transmitted accurately, by the masorah, from earlier generations. That masorah is one consisting of a way of thinking halachically, as well as attitudes, perspectives, and style, vis-à-vis the wording of brachot.