Despite extensive research, no applying maggid shiur met the standards of the bochurim at the yeshiva in Lubavitch. At that point, they recommended taking one of their own, the bochur R. Shmuel Nissenevitch, which the Rebbe Rashab approved with a metaphor.
R. Shmuel Nissenevitch was born in Borisov (approx. 5652) and was thus known as R. Shmuel Borisover (not be confused with the famous earlier chossid, R. Shmuel Ber Borisover). A talmid of Tomchei Temimim in Lubavitch, he was appointed to serve as a Magid Shiur in Lubavitch while still a bochur. With his unique combination of geonus and bittul, R. Shmuel raised a generation of Chassidishe talmidei chachomim. He tragically passed away at a young age on 11 Iyar, 5682.
When a maggid shiur was needed in Lubavitch during its developmental years, talmidei chachomim from across the country would be invited come to Lubavitch and deliver a model shiur. The shiur would be said before a small group of lamdanim from the senior bochurim, who would then decide if he was up to standard.
One time, after being dissatisfied with several applicants, they suggested to the Rebbe Rashab to take instead the bochur in yeshiva Shmuel Nissenevitch, whom they knew to be an outstanding lamdan. The Rebbe agreed and told them, “When a bear is hungry, it gnaws at its own paws…”
R. Shmuel was an exceptional gaon, yet incredibly unassuming and humble. He taught bochurim in the “Shiurim” who were 15-16 years old, and after learning with him for a year the bochurim were ready to learn on their own in Schedrin and Lubavitch.
His style was of logical reasoning without excessive pilpul, and he would say that after understanding a sugya thoroughly, any contradictions fall away. He would often say the meforshim’s explanations on his own, without having learned them.
R. Zalman Shimon Dvorkin recalled R. Shmuel as an incredible genius, and said he was capable of answering questions posed by R. Akiva Eiger on the spot.
R. Avrohom Mayor shared how during one shiur, the Frierdiker Rebbe, then the menahel of Tomchei Temimim, entered the room. All the talmidim were overcome with awe and fear, but R. Shmuel was so absorbed in what he was teaching that he did not notice his presence. When the talmidim motioned to him about it, he didn’t stop the shiur, rather he got more involved in the Gemara, sharing even deeper insights than ever before.