Another interpretation of "Who is like the wise person?" (Ecclesiastes 8:1): This refers to a disciple of a sage. "And who knows the interpretation of a matter?" - at the time when he knows how to expound his Mishnah. "A person's wisdom lights up his face" - at the time when he is asked a question and answers. "But the boldness of his face is changed" - at the time when he is asked a question and does not answer.
Who Is Like the Wise Person - The Disciple Whose Face Shines
Midrash Tanchuma Buber, Chukat 19:1
[ד"א מי כהחכם. זה תלמיד חכם, ומי יודע פשר דבר, בשעה שהוא יודע לפרש משנתו, חכמת אדם תאיר פניו, בשעה שנשאל ומשיב, ועוז פניו ישונה, בשעה שהוא נשאל ואינו משיב.