Hope everyone had a great Shavuos. Still pressed for time, but will try to post a little. There is a mitzvah d’oraysa to obey the words of a Navi. Minchas Chinuch (516) asks why is it that any time a person violates any mitzvah, he/she is not also guilty of a secondary issur of disobeying the words of a Navi? Since every mitzvah was transmitted to us through Moshe Rabeinu, the greatest of Nevi’im, by disobeying any mitzvah we have also disobeyed a Navi!
I would take the Minchas Chinuch’s question a step further. The M.C. presents a machlokes between Tosfos and the Rambam whether the mitzvah of listening to the Navi applies only to that which the Navi heard directly from G-d, or even to insights which the Navi thought of him/herself. If the mitzvah to obey the Navi applies even to ideas the Navi did not hear directly from G-d, then if someone violates a takana which was instituted by a Navi, why would this also not be tantamount to violating the din d’oraysa of listening to a Navi? For example, kri’as haTorah is a takana which was instituted by Moshe Rabeinu. Would skipping kri’as haTorah and violating that takanah also be a violation of the din d’oraysa of obeying a Navi?
R’ Soloveitchik answered the Minchas Chinuch’s question by suggesting that the mitzvah in question does not apply to the Navi as a gavra, a persona, but applies to words of nevuah. By definition, a mitzvos and takanos are categorically distinct from words of nevuah (see also the Rogatchover Mh”T Yesodei haTorah 9:1)
Be that as it may, given the Minchas Chinuch, I thought we might be able to answer R’ Elchanan’s question regarding the extra day of preparation before mattan Torah that Moshe added “mda’ato”. R’ Elchanan asked what authority Moshe had to offer his interpretation when the mitzvah of “lo tasur”, the “license” for Rabbinic interpretation, had not yet been given. R’ Elchanan postulated that Rabbinic authority must not be rooted not in a specific commandment like “to tasur”, but more generally in the Rabbis ability to intuit G-d’s will. I think R’ Elchanan is right that in this case Moshe intuited G-d’s will, but I’m not sure we can generalize from Moshe to Rabbinic authority in general. Perhaps Moshe’s authority in this case stemmed not from his role as Moshe “Rabeinu”, Moshe the Rabbi or chacham, but rather stemmed from Moshe’s role as Navi. It is not the Rabbi or chacham whose authority stems from some transcendent insight into G-d’s will – that is the role of the Prophet.