Question

How are you, Rabbi?
A question came to me—maybe you can help me. What is the source for relying on the words of the Sages and rabbis throughout the generations the way we rely on the Torah itself? I can understand why regarding the Torah and the Oral Torah, since according to the tradition they came through direct revelation—but what about the rest of the world of Torah: the commentators, the mystical tradition, and so on? Which interpretations can be accepted and which cannot? Is there perhaps a sufficient source from the Torah for this, or is it a matter of what seems reasonable? When, after all, does one need to accept the authority of the Sages if it is based only on reasoning?