Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 174
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 174, with English translation by Maimonides (Rambam).
לשמוע מכל בית דין הגדול שיעמדו להם לישראל, שנאמר: "ועל המשפט אשר יאמרו לך--תעשה" (דברים יז,יא).
To obey the High Court regarding all [the ordinances] they establish for Israel, as [Deuteronomy 17:11] states: "Carry out the judgment which they render for you."