Isidor Grunfeld

Isidor Grunfeld (1900–1975), also known by his Hebrew name Yishai ha-Kohen Grunfeld, was a dayan (rabbinical judge) and author who was associated with the London Beth Din (rabbinical court). He is best known for several popular works on Jewish law, and for his translations of the works of Samson Raphael Hirsch.

Born in the Bavarian town Tauberrettersheim, he was educated in German yeshivot and acquired a legal degree after attending several universities. He married teacher and Bais Yaakov educator Dr Judith Rosenbaum in 1932. He worked as a lawyer in Würzburg until 1933, when the Nazis' rise in power prompted him to move to London. After initially working in the legal field, he underwent rabbinical training and became a member of the London Beth Din.

In 1954 a heart attack led to his early retirement from the London Beth Din. After retirement he published a number of books on Jewish law: on the Sabbath, kashrut (Jewish dietary laws), the laws of shmita and yovel (the Sabbatical year and Jubilee) and inheritance law. In addition, he translated some of the works of 19th century German-Jewish leader Samson Raphael Hirsch (1808-1888), namely Horeb and Judaism Eternal, and he wrote on the influence of Hirsch in Three Generations and the introduction to Horeb as well as an introduction to the translation of Hirsch' Torah commentary by Levy.