Parsha Mitzvot: Shofetim: Mitzvah 492 – Concept 578
“According to the teaching that they will teach you and according to the judgment that they will say to you, shall you do; you shall not deviate from the word that they will tell you, right or left.” (Deuteronomy 17:11) We are commanded to act in accordance to the rulings of the Great Sanhedrin. (Rambam, Hilchot Mamrim – The Laws of Insurgents)
There are three levels to the teaching duties of the Sanhedrin: 1) The protecting and furthering rules which they make for the practice of Torah, 2) The results of research and interpretation of the Torah based on the traditional hermeneutical 13 Midot through which we derive laws from the Torah, and 3) The further handing down the traditions they have received.
For all three the Torah demands the most unswerving obedience, active and abstaining, so at the base of all Rabbinic law there lies a Biblical obligation, and acting against a law of the Rabbis is no less than transgressing a Divine command and prohibition.
This is how we can say a blessing, “Who has sanctifed us with His commandments,” before performing a Rabbinic Mitzvah. (Rabbi Samson R. Hirsch)