The Navi is obviously very special, since Hashem has chosen him for this function. How are we to know if he is truly Hashem’s choice? Apparently, the credentials of this tzaddik, righteous person, are impeccable, characterized by positive attributes and virtues to which everyone agrees. Nonetheless, everyone has his personal opinion and his own litmus test. What passes muster for one person does not necessarily pass muster for another. Is there a clear- cut criteria which define a righteous leader? Rashi comments that he must be mumchah hu lach, proven to you, to be a tzaddik gamur, such as Eliyahu HaNavi, whose spiritual distinction is undisputed. Indeed, he was within his rights, and he acted appropriately when he overrode a Rav of the Torah. He brought a korban, sacrifice, on Har Carmel, away from the Bais Hamikdash. In this instance, Eliyahu suspended the law, because it was necessary. Only someone of his caliber, however, could act in this matter.
Horav Leizer Brody, Shlita, relates the story of two yeshivah students who debated among themselves, considering the virtues and spiritual/intellectual distinction of their respective rebbeim. Each one, of course, posited that his respective Rosh Yeshivah was greater than the other’s. Word of this debate reached the ears of the Mashgiach of the yeshivah, who summoned both bachurim to his office. He began the conversation by asking one of the students to recite the tefillah of Atah Chonantanu, “You have graced us with intelligence” (a prayer recited in the Motzoei Shabbos Shemoneh Esrai that distinguishes between various contrasts) by heart. He proceeded to recite the tefillah without error. The Mashgiach then turned to the other bachur and asked him to recite Va’todeinu, a similar prayed recited on the occasion that Yom Tov falls on Motzoei Shabbos. The two tefillos are parallel in nature, but the latter prayer draws distinction between Shabbos and Yom Tov, while Atah Chonantanu presents a contrast between Shabbos and chol, weekday. This time the student had difficulty remembering every word in perfect sequence. (Practically, Atah Chonantanu is recited weekly, while Vatodeinu is recited a few times a year and not every year.)
The Mashgiach said to the student, “Do not be embarrassed that you are unable to recite Vatodeinu by heart, but everyone recites Atah Chonantanu without a problem. Everyone has the ability to distinguish between kodesh and chol, sacred and mundane. Not everyone has the capacity, however, to distinguish between kodesh (Shabbos) and kodesh (Yom Tov). Your Rebbe understands the tendencies of your soul; he is acutely aware of your disposition and propensity. Likewise, your friend’s Rebbe is aware of his students’ individual proclivities and impulses. From a spiritual perspective, your respective Rebbeim understand the source of your neshamos and how Hashem watches over each one of you. One cannot determine which Rebbe is greater; rather, each student is best served by his individual Rebbe.”
This is quite possibly what Rashi means when he says, Mumchah hu lach; “he is proven to you.” Each talmid has his individual Rebbe that “works for him.” His Rebbe understands what “makes him tick,” how to reach him and how to encourage him to shteig, grow in Torah, yiraas Shomayim and middos tovos. Not every student is a perfect “fit” for someone else’s Rebbe. Each one must seek the Rebbe who is mumchah, proven, for him.
The average person is unable to determine the distinction of a tzaddik. He can, however, ascertain the Rebbe who was the greatest influence on him, who inspires him most, and to whom his soul gravitates. That Rebbe is his tzaddik. Furthermore, the Rebbe who understands his talmid’s deficiencies, needs, and growth potential, as well as how he can engender this growth, is the Rebbe who is best aligned with his soul.
