Rambam: Rotseah uShmirat Nefesh, Chapter 12

Rabbi Yaakov Moshe Wolberg, a renowned Talmudic scholar, served for several decades as an instructor in Talmud at the Oholei Torah Yeshiva in New York, and later at Yeshiva Lubavitch Manchester, U.K. and now serves as Rosh Yeshiva in Kfar Chabad.