Reb Folle Kahn relates:
Reb Mendel Diskin was a teacher in the Yeshivah of Tomchei Temimim (the Chabad Yeshiva). Once on Simchas Torah the Rebbe Rashab said: “When Moshiach comes, he will sit Mendel with a gaon (Torah genius) of the misnagdim to learn Tanya with him.” At that moment Reb Mendel was sitting before the Rebbe Rashab.Explanation and lesson: There is a special light in the teachings of Chassidus, and when Moshiach comes, this light will become undeniably clear, such that even those who had earlier opposed it will come to accept and revere it. This is only understandable, considering that the revelation of Chassidus is a foretaste of the teachings of Moshiach. Accordingly, Moshiach will bring even a gaon who had not learned Chassidus to recognize the special quality of one who has learned Chassidus, even if that person is not a genius.Shemu’os V’Sipurim, Vol. 1, p. 119.