Leket Yosher is a 15th-century work by Rabbi Yosef ben Moshe that records the customs and legal opinions of his teacher, Rabbi Yisrael Isserlein. The work also includes a biography of Isserlein and several of his responsa. In an introduction, the author writes that he came to compile the book after receiving questions about his teacher’s opinions on legal matters while traveling. When Rabbi Yosef was not able to easily answer these questions, he realized that it would be valuable to record his teacher’s practices and opinions so that others could easily learn from them. Leket Yosher was first published from manuscript in 1903.