Many Rebbes and Tzaddikim studied and taught a shiur in Ohr HaChaim on Leil Shishi, Thursday night, as a hachana, a preparation, for Shabbos Kodesh, including: Rav Moshe Yehoshua and Rav Yisrael of Vizhnitz; Rav Menachem Mendel of Deeshz; Rav Avrohom Elimelech of Karlin HY”D; Rav Yochanan of Karlin who said, “besides the fact that it uplifts all who study it, it is a preparation for Shabbos and it is a segulah to uplift the spiritual levels for all who engage in learning the Ohr HaChaim, each according to their respective level,” and that “Az MiLernt Ohr HaChaim HaKadosh Donerstog BeiNacht Hat Der Yedid Nefesh an underen ta'am! — If you study the holy Ohr HaChaim Thursday Night then your song Yedid Nefesh on Shabbos will have a different feel and flavor!"
(Rav Avrohom of Slonim, Rav Sholom Noach of Slonim, Rav Shamshon Aharon of Teplick, Rav Aharon Yehudah Leib Vilner of Sheeris haPleita & Kloizenberg) (Ner Maarvi, page 214).
