Moses Isserles (or Moshe Isserlis) (1520 (Cracow, Poland) - May 1,1572), was an eminent Ashkenazic Rabbi, Talmudist, and Posek, renowned for his fundamental work of Halakha (Jewish law), entitled HaMapah (lit., "the tablecloth"), an inline commentary on the Shulkhan Aruch (lit. "the set table"). He is also well known for the Darkhei Moshe, a commentary on the Tur. Moses Isserles is also referred to as "the Remo" or Rema רמ״א, the Hebrew acronym for Rabbi Moses Isserles.
Moshe was born in Cracow. His father, Israel (known as Iserl), was a prominent Talmudist, said to have been independently wealthy, and probably headed the community; his grandfather, Jehiel Luria, was the first Rabbi of Brisk. (In an era which preceded the use of surnames, Moses became known by his patronymic, Isserels - corrupted in English to Isserles.) He studied in Lublin under Rabbi Shalom Shachna, who became his father-in-law; among his fellow pupils were his relative Solomon Luria (Maharshal), and Chayyim b. Bezalel, an older brother of the Maharal. Rema’s wife died young, at the age of 20 and he later established the "Rema Synagogue" in Cracow in her memory (originally his house, built by his father in his honor—which he gave to the community). He later married the sister of Joseph ben Mordechai Gershon Ha-Kohen.
He returned to Cracow about 1550, when he established a large yeshiva and, being a wealthy man, supported his pupils at his own cost. In his teaching, he was opposed to pilpul and he emphasized simple interpretation of the Talmud. In 1553 he was appointed as dayan; he also served on the Council of the Four Lands. He became a world-renowned scholar and was approached by many other well-known rabbis, including Yosef Karo, for Halachic decisions. He was one of the greatest Jewish scholars of Poland, and was the primary halakhic authority for European Jewry of his day. He died in Cracow and was buried next to his synagogue. On his tombstone is inscribed: "From Moses (Maimonides) to Moses (Isserles) there was none like Moses". Until the Second World War, thousands of pilgrims visited his grave annually on Lag Ba'omer, his Yahrzeit (date of death).
Not only was Rema a renowned Talmudic and legal scholar, he was also learned in Kabbalah, and studied history, astronomy and philosophy. He taught that “the aim of man is to search for the cause and the meaning of things” ("Torath ha-Olah" III., vii.). He also held that "it is permissible to now and then study secular wisdom, provided that this excludes works of heresy... and that one [first] knows what is permissible and forbidden, and the rules and the mitzvot" (Shulkhan Aruch, Yoreh De'ah, 246, 4). Maharshal reproached him for having based some of his decisions on Aristotle. His reply was that he studied Greek philosophy only from Maimonides’ Guide for the Perplexed, and then only on Shabbat and Yom Tov (holy days) - and furthermore, it is better to occupy oneself with philosophy than to err through Kabbalah (Responsa No. 7).
Rema is buried in the Old Jewish Cemetery in Crakow.
Darkhei Moshe (דרכי משה) is a commentary on the Tur as well as on the Beth Yosef, which is Yosef Karo's commentary on the Tur and the work underlying the Shulkhan Aruch. Isserles had originally intended the Darkhei Moshe to serve as a basis for subsequent halakhic decisions. As such, in this work he evaluates the rulings of the Tur - which was widely accepted among the Ashkenazim and Sephardim - comparing these with rulings of other halakhic authorities. The Beth Yosef was published while Isserles was at work on the Darkhei Moshe. Recognizing that Karo's commentary largely met his objectives, Isserles published the Darkhei Moshe in a modified form. An abridgement of the original work is published with the Tur; the complete version of the Darkhei Moshe is published separately.
HaMapah (המפה) is written as a gloss to the Shulchan Aruch of Yosef Karo, discussing cases where Sephardi and Ashkenazi customs differ. (Hamapah is the "tablecloth" for the Shulkhan Aruch, the "set table".) Karo had based his normative positions on three authorities: Maimonides, Asher ben Jehiel (the Rosh), and Isaac Alfasi (the Rif). Of these, only Asher ben Jehiel had non-Sephardic roots, having lived most of his life in Germany before moving to Spain, but even so, his work is largely Sephardic in orientation. Isserles thus created a series of glosses, in which he supplemented Karo with material drawn from the laws and customs (Minhagim) of Ashkenazi Jewry - chiefly based on the works of Yaakov Moelin, Israel Isserlein and Israel Bruna. All editions of the Shulchan Aruch since 1578 include HaMapah embedded in the text (introduced by הגה Hagahah, "gloss"), and distinguished by a semi-cursive "Rashi script". Today, "Shulchan Aruch" refers to the combined work of Karo and Isserles. This consolidation of the two works strengthened the underlying unity of the Sephardi and Ashkenazi communities. It is through this unification that the Shulkhan Aruch became the universally accepted Code of Law for the entire Jewish people.
Rabbi Isserles also wrote: