When The Student Becomes The Rebbe

The Mahari Bruna (born 1400 in Germany) was asked the following question: If a student surpasses his rebbe in Torah scholarship, does he still have to honor him? Of course he still has to treat his former rebbe respectfully, as he would any talmid chacham. However, does the former student still have to accord his past rebbe with the honor reserved for a rebbe?
The Mahari Bruna said that perhaps an answer can be derived from the Gemara, which declares (Eiruvin 92a), “If Rebbe Yehudah haNasi did not teach it to Rebbe Chiya, how would Rebbe Chiya know it?” Rashi explains that Rebbe Chiya was a student of Rebbe Yehudah haNasi. The Gemara seems to be saying that Rebbe Chiya’s primary source of Torah knowledge was Rebbe Yehudah.
Yet a Gemara in Niddah (14b) quotes Rebbe Chiya as telling Rebbe Yehudah, “Even you are treating this like a stain.” Tosfos notes that this statement seems to be disrespectful. A talmid should not address his rebbe by the plain term “you.” An honorific title should be added or the statement should be rephrased. Tosfos says we would have expected Rebbe Chiya to say, “Even you, Rebbe, are treating this . . .” Tosfos concludes from this that Rebbe Chiya excelled to the point that he became an equal to his rebbe. This phenomenon is referred to as becoming a talmid chaver. Now that Rebbe Chiya was Rebbe Yehudah haNasi’s peer, he no longer had to address him with the honorific title of “Rebbe.” Every rebbe who sincerely cares for his students would feel pride when a former student becomes equal to or greater than himself.