||Responsa by R. Nissim b. Reuben Gerondi, (known from the acronym of Rabbenu Nissim as the Ra-N;-1310–?1375), one of the most important Spanish talmudists. R. Nissim's family originated in Cordova and settled first in Gerona, where he is thought to have been born, and then in Barcelona, which became his permanent place of residence. Few biographical details are known of him. He never held any official rabbinical post, even though in fact he fulfilled all the functions of a rabbi and dayyan in his community. Furthermore, many takkanot enacted in Spain originated with him, and his reputation as an authoritative posek was such that he received queries from as far as Erez Israel and Syria. He is also known to have served as a physician in the royal palace. Because of a calumny, the date and causes of which are not certain, he was imprisoned for some time. It is also known that in 1336 he wrote a Sefer Torah for his own use, which became well known and served as a model. This Sefer Torah was moved from place to place until it reached Tiberias, where it was preserved until recently. R. Nissim's main teacher, apart from his father, was R. Perez ha-Kohen, with whom he was in close correspondence; R. Nissim even assisted him to become accepted as rabbi of Barcelona (after 1349). It seems that R. Nissim's main activity in his community was as head of the Barcelona yeshivah. Among his chief pupils were R. Isaac b. Sheshet Perfet, who frequently quotes him, mostly anonymously, R. Hasdai Crescas, R. Joseph Habiba, and R. Abraham Tamakh.
R. Nissim's renown rests chiefly on his halakhic works. His method and system were solidly founded in accordance with the tradition of learning acquired from the school of Nahmanides, R. Solomon b. Abraham Adret, R. Aaron ha-Levi of Barcelona, and their contemporaries, and though his works contain many sayings of these scholars without naming them, he adapted their words, crystallized them, and added much of his own so that his works are among the best produced by this school of learning. One of his main works is a commentary on the halakhot of R. Isaac Alfasi to the Talmud. It seems that all the parts of this work have been preserved, and all have been published on the margin of R. Alfasi's commentary beginning with its first printed editions down to the present day.
This commentary comprises the tractates Shabbat, Pesahim, Bezah, Rosh Ha-Shanah, Yoma, Ta'anit, Megillah, Sukkah, Ketubbot, Gittin, Kiddushin, Shevu'ot, Avodah Zarah, Hullin, and Niddah. He also wrote novellae to the Talmud, of which up to the present the following have been published: Gittin (Constantinople, 1711), Niddah (Venice, 1741), Hullin to the end of chapter 8 (in: Hamishah Shitot, Sulzbach, 1762), Bava Mezia (Dyhrenfurth, 1823), Shevu'ot (Venice, 1608, at the end of the responsa of R. Moses Galante), Rosh Ha-Shanah (1871), Avodah Zarah (1888), Mo'ed Katan (1937), Bava Batra (1963), Eruvin (1969), and Pesahim (1970).
His commentary to the tractate Nedarim, which is his best-known work, is published in all the usual editions of the Talmud and serves as the standard commentary to this tractate instead of that of Rashi. Some of his novellae to the Talmud still remain in manuscript, but most of them have been repeatedly republished, since they are among the works most acceptable to scholars of all countries and times. His commentaries to Alfasi differ from those to the Talmud in that they aim at giving the halakhic ruling, and in fact they have no real literary connection with R. Alfasi, with whom he frequently disagrees. The novellae to tractates Megillah, Shabbat, Ketubbot, and Sanhedrin published under Nissim's name are not by him. They represent one of the most difficult problems connected with the study of R. Nissim's works and teachings, as it is definite that a generation and more before him there lived in Barcelona another scholar with the same acronym - Ra-N (whose personal name is not certain), and whose works to several talmudic tractates have been recently published. Only 77 of R. Nissim's responsa are extant (Rome, 1545; and Constantinople, 1548 from a different Ms. and thereafter in many editions); also a book of 12 sermons (Constantinople 15331 and frequently), of a decidedly anti-philosophical character though written in the style of philosophical literature; and a commentary on the Pentateuch of which the section on Genesis has been published (1968). The publication of the commentary to the Pentateuch has removed the few doubts that remained among some scholars as to whether R. Nissim is the Ra-N of the book of sermons ascribed to him or whether they were perhaps written by the other scholar of the same name. Discernible in both these works is R. Nissim's strong desire to prove the superiority of prophecy and Bible over philosophy, and thereby to strengthen the people's faith and their spiritual ability to bear up during the difficult periods of persecution and polemics of those times. He also wrote piyyutim and poems, some of which have been preserved and published.