Rabbi Asher ben Yehiel (1250 - 1327) was an eminent Rabbi and Talmudist best known for his abstract of Talmudic law. He is often referred to as Rabbenu Asher, "our Rabbi Asher" or by the Hebrew acronym for this title, the ROSH (literally "Head"). The Rosh was born in western Germany and died in Toledo, Spain. His family was prominent for learning and piety, his father Yechiel was a Talmudist, and one of his ancestors was Rabbi Eliezer ben Nathan (the RaABaN). Asher had eight sons, the most prominent of whom were Yehuda and Yaacov, author of the Arbaah Turim, a code of Jewish law. His primary teacher was the Tosafist Rabbi Meir of Rothenburg, then in Worms. In addition to his studies, ROSH worked in money lending, and according to his own statement, was independently wealthy.

In 1286, the German Emperor had instituted a new persecution of the Jews, and Rabbi Meir left Germany, but was captured and imprisoned. The ROSH raised a ransom for his release, but Rabbi Meir refused it, for fear of encouraging the imprisonment of other rabbis. Thereafter the Rosh assumed Rabbi Meir's position in Worms. He was, however, forced to emigrate. After leaving Germany, he first settled in southern France, and then in Toledo, Spain, where he became rabbi on the recommendation of Rabbi Solomon ben Aderet (RaShBA). Rabbenu Asher's son Yehuda testified to the fact that he died in poverty. Rabbeinu Asher died in Toledo on 9 Cheshvan 5088 (1327 CE).

Rabbenu Asher possessed "methodical and systematic" Talmudic knowledge, and was distinguished for his ability to adumbrate long Talmudic discussions. The ROSH, influenced by his teacher Rabbi Meir, was averse to lenient decisions in halakha, even when theoretically justified. Several of his rulings which may appear lenient, are actually strictures: his decision against praying more than three times a day is, in fact, limiting. Similarly, his assertion that the phrase halacha leMoshe miSinai, "an oral law revealed to Moses on Sinai", does not always bear a literal meaning but often signifies a universally adopted custom, is not usually taken as a liberal interpretation. The ROSH was, however, known for his independent legal reasoning: "We must not be guided in our decisions by the admiration of great men, and in the event of a law not being clearly stated in the Talmud, we are not bound to accept it, even if it be based on the works of the Geonim." For instance, the ROSH ruled that the liturgy of the Geonim was not subject to the Talmudic rule against change in the prayers.

Rabbenu Asher’s best known work is his abstract of Talmudic law. This work specifies the final, practical halakha, leaving out the intermediate discussion and concisely stating the final decision. It omits areas of law limited to Eretz Yisrael, such as agricultural and sacrificial laws, as well as the aggadic portions of the Talmud. Asher's son Jacob compiled a list of the decisions found in the work, under the title Piskei Ha-ROSH (decisions of the ROSH). Commentaries on his Halachot were written by a number of later Talmudists. In yeshivot, this work is studied as a regular part of the daily talmud study. It is not well known, but the work is actually not a commentary on the Talmud but is rather a commentary on the Rif, and always starts with the text of the Rif. This work resembles the Hilchot of the Rif (Rabbi Isaac Alfasi), but differs in quoting later authorities such as Maimonides, the Tosafists and Alfasi himself. Rabbenu Asher's work superseded Alfasi's within a short time and has been printed with almost every edition of the Talmud since its publication. This work was so important in Jewish law that Rabbi Yosef Karo included the ROSH together with Maimonides and Isaac Alfasi as one of the three major poskim (decisors) considered in determining the final ruling in his Shulkhan Arukh.

Rabbi Yaacov ben Asher, also known as Baal HaTurim, was born in Cologne, Germany 1269 and died in Toledo, Spain 1343. He was an influential Medieval rabbinic authority. He is often referred to as the Baal HaTurim ("Master of the Rows"), after his main work in Halacha (Jewish Law), the Arbaah Turim ("Four Rows"). The work was divided into 4 sections, each called a "tur," alluding to the rows of jewels on the High Priest's breastplate. He was the third son of the Rosh, Rabbi Asher ben Yehiel. Besides his father, who was his principal teacher, Rabbi Yaacov ben Asher quotes very often in the Turim his elder brother Yehiel, once his brother Yehuda, and once his uncle Rabbi Chaim.

His works include Arbaa Turim, one of the most important halachic books of all times. Sefer ha-Remazim, or "Kitzur Piske ha-Rosh", an abridgment of his father's compendium of the Talmud, in which he condensed his father's decisions. Rimze Baal ha-Turim, a commentary on the Pentateuch, which is printed in virtually all Jewish editions of the Pentateuch. This concise commentary consists of mystical and symbolical references in the Torah text, often using gematria and acronyms as well as other occurrences of particular words elsewhere in the Torah. Perush Al ha-Torah, a less known commentary on the Pentateuch, taken mainly from Nachmanides, but without his Kabbalistic and philosophical interpretations. Jacob quotes many other commentators, among them Saadia Gaon, Rashi, Joseph Dara, and Abraham ibn Ezra.