Likutei Sichos vol 27, Nissan 2, Rabbi Chaim Wolosow
https://www.torahrecordings.com/likutei-sichos/027/002_001 The Rebbe Rashab’s Revolution in the Study of Chassidus The Rebbe explains the Rebbe Rashab’s great innovation: Chassidus must be learned like Nigleh—with effort, questions, chavrusa, and real understanding. “The ksovim I leave you” means they must be taken through toil until Chassidus becomes the student’s own Torah.