Rav Yeshayah Menachem Mendel Avigdor Av Beis Din Of Cracow

Author of the Heter Iska, he served as the Rav and Av Beis Din in Shebreshin (Szczebrzeszyn), Bendin, Ludmir and Cracow. It was during his tenure in Bendin that he first formulated the Heter Iska which is used to help circumvent the prohibition of loans with interest or ribbis and the heter iska nusach contains till this day the formula "על פי תיקון מהר"מ ז"ל" or "על פי תיקון מור"ם ז"ל מקראקא" to commemorate his authorship. It was widley publicized in Siman Mem (40) through Rav Shmuel ben David haLevi's Segal's sefer Nachlas Shiva, who was the son and talmid of the Taz.

He authored the sefer BeUrim Kibdu es Hashem on Rashi's commentary for Chumash. The famed Rav Eliyahu Luntz Baal Shem was his disciple.