Jacob Emden, also known as Ya'avetz (June 4, 1697 – April 19, 1776), was a leading German rabbi and talmudist who championed Orthodox Judaism in the face of the growing influence of the Sabbatean movement.
He was acclaimed in all circles for his extensive knowledge.
"Thus Moses Mendelssohn, founder of the Jewish Enlightenment movement, wrote to him as 'your disciple, who thirsts for your words.' Although Emden did not approve of the Hasidic movement which evolved during his lifetime, his books are highly regarded amongst the Hasidim.
Thirty-one works were published during his lifetime, ten posthumously, while others remain in manuscript."Emden was the son of the Chacham Tzvi, and a descendant of Elijah Ba'al Shem of Chelm.
He lived most his life in Altona (now a part of Hamburg, Germany), where he held no official rabbinic position and earned a living by printing books.
His son was Meshullam Solomon, rabbi of the Hambro Synagogue in London who claimed authority as Chief Rabbi of the United Kingdom from 1765 to 1780.The acronym Ya'avetz (also written Yaavetz) stands for the words Yaakov (Emden) ben Tzvi (his father's name) (Hebrew: ???? (?????) ?? ??? - ???"?).