Rebbe Reb Shmelke Nikolsburger was a talmid of the great Mezritcher Maggid, Rebbe Reb Dov Ber. In the sefer Shemen HaTov the following story is cited in the name of the Apta Rav, mechaber of Ohev Yisrael:
Originally, Rebbe Reb Shmelke and his brother Rav Pinchas Horowitz, mechaber of the Haflo’a, were both talmidim of the Vilna Gaon. The Gra decided to gather a minyan and convene a Bais Din to sit and decree preventing anyone from marrying any of the Mezritcher Maggid’s talmidim. Counted among the Dayonim in this Bais Din were Rebbe Reb Shmelke and the Haflo’a. When word of the pending decree reached Rebbe Reb Ber’s ears he sent his talmidim, Rav Avrohom Kalisker and Rebbe Reb Zusha, to Vilna to attempt to prevent the decree. He advised them and gave them the following idea how to draw near the Gra: “When you come to Vilna the Gaon will be dealing with certain Tosafos and studying it with his talmidim and discussing its meaning. I will teach you a way to explain this Tosafos and when you present the solution to the Gra, he will be impressed and draw you near.”
And so it was. When the Vilna Gaon asked the identity of the two anonymous strangers who were obviously Talmidei Chachomim of some caliber since they could explain such a difficult Tosafos so well, they told him the truth, that they were talmidim of Rebbe Reb Ber, the Maggid of Mezritch. And so there was no decree, Rebbe Reb Shmelke and his brother the Haflo’a both decided to leave for Mezritch and see for themselves who this Maggid was.
In the sefer Maasei Tzaddikim it describes their first encounter with the Maggid: When Rebbe Reb Shmelke suggested they travel to the Maggid, his brother countered, “And what will be with all the bitul Torah on the way?”
“I have heard that he is a great Gaon and that he is great in Torah as well,” answered Rebbe Reb Shmelke, and so his brother agreed and they traveled to Mezritch. They were extremely disappointed by their initial encounter on Erev Shabbos when, instead of engaging them with Divrei Torah and a pilpul as they expected, the Maggid told them he needed to prepare to greet the Shabbos Queen and dismissed them. Likewise his Sholosh Seudos Torah disappointed them, as they expected a pilpul and a discourse as they were accustomed, and not Chassidus. They decided to take leave of the Maggid.
“Before you go on your way, please take leave of Rebbe Reb Zusha as well,” asked the Maggid.
And so they both went to the Bais Medrash and found Rebbe Reb Zusha, who challenged them, “It says in the Medrash in the name of Chazal that if your Rav is compared to an angel then you can ask Torah from his mouth and study, and if not, then no, but I ask you – have you ever met or seen an angel? If you cannot recognize an angel, then how would you know if your Rav is comparable to one and whether or not you can accept Torah from him?”
The two brothers agreed, and said to one another that such profound wisdom from Rebbe Reb Zusha proves that his master and teacher the Maggid must truly be as an angel great in Torah. They stayed and became devoted talmidim. (Menora HaTehora p. 9 #1 and #2)
