Rabbi Gershom Meor Hagolah: (10th-11th Centuries, Ashkenazic)

A disciple of Rabbi Hai Gaon, Rabbi Gershom’s famous enactments, known as Cherem DeRabbainu Gershom, continue to have a great impact on Jewish life. The best known of these is the dictum that a man may not be married to two women simultaneously, an act permissible according to Biblical law. The reason for his enactment was to prevent strife between the two wives, which seemed to be a problem in Rabbi Gershom’s time. Although this decree was originally set to expire in the year 5000 (1240 CE), Ashkenazic Jews extended the restriction, thus giving it the force of eternal Jewish law.

Another decree, related to the first, is the limitation of the husband's power to divorce his wife. Under Biblical law, a divorce may be effected against her will. However, at that time, due to the increasing abuse of this rule by men who arbitrarily divorced their wives, Rabbi Gershom took this step to protect women. An exception is the much-misunderstood Heter Meah Rabbanim, a dispensation given by 100 rabbis in three countries for a man to marry a second wife while still technically married to the first one. Such an exception is only performed in extremely limited circumstances, such as when the wife committed adultery, in which case the Torah prohibits the marriage to continue. If, at that point, the wife refuses to receive a get, a divorce document, one may be written for her and deposited with a Jewish court. She is then notified that any time she wishes, she may receive the get and be free of the marriage. Then, and only then, may the husband initiate the Heter Meah Rabbanim process, which allows him to remarry. Clearly, this process is not a method for a husband to escape marriage while leaving his lawful wife in limbo.

A third of Rabbi Gershom's decrees is that one may not read sealed letters sent to another person. Although such reading is also forbidden under the Biblical injunction against gossip, (Lo Selech Rachil B‘Amecha — Leviticus 19:16) to emphasize its severity Rabbi Gershom imposed a cherem, a ban, on such behavior. It then became customary to write on the outside of letters the Hebrew acronym Upagin Deragmah, based on a verse in Ecclesiastes 10:8, which stands for "One who breaks a fence (a ban) of Rabbi Gershom should be bitten by a snake." Rabbi Gershom also enacted the decree that if a Jew converted to Christianity and subsequently repented, he should be welcomed back to the community and not encounter any discrimination. Rabbi Gershom's disciples were the teachers of Rashi.

Rabbi Nassan of Rome: (11th Century, Ashkenazic)

Rabbi Nassan wrote the Aruch, the first dictionary of obscure words in the Talmud, grouped in alphabetical order. The work was accepted by all scholars, both Sephardic and Ashkenazic, and is quoted by Rashi and Tosafos. In the course of defining words, the Aruch gives new insights into Talmudic topics, some of which are accepted as definitive halacha. For example, in discussing the word heses, an oath imposed by the rabbis of the Talmud in specific instances, the Aruch describes the elaborate procedure taken by the court in administering a Biblical oath. When a litigant swears a Biblical oath, a coffin is brought into the room, sackcloth and dirt are spread around, balloons are popped, and candles are lit and then extinguished. The one swearing holds a Torah scroll, and a shofar is blown as the oath is taken. (Currently, due to the severity of possibly swearing falsely, there is great reluctance to impose such oaths in court, and only rabbinic oaths, which are less severe, are administered.) The Aruch remains immensely popular to this very day.

Rabbi Shlomo Ben Yitzchak (Rashi): (1040-1105, Ashkenazic)

The famous name Rashi stands for Rabbi Shlomo Yitzchaki, or Rabban Shel Yisrael, the teacher of the Jewish people. The appellation Teacher of the Nation has been given to a select few leaders throughout Jewish history, among them Moshe Rabbeinu (Moses) and Rabbeinu HaKodosh (Rabbi Judah HaNasi). Rashi stands in such august company because no other individual in the last 1,800 years has played such a major role in making the Torah's wisdom accessible to as many Jews.

A number of well-known legends surround Rashi's birth and life. Rashi's father, Rabbi Yitzchak, was a diamond merchant. Once, he came into possession of a spectacular gemstone that the Church wanted as a centerpiece for a statue. Despite much pressure, and promises of incredible sums of money, Rabbi Yitzchak refused to sell the diamond. When Church officials lured him onto a boat and threatened him with death if he refused to sell, only then did Rabbi Yitzchak agree to part with the precious stone. While standing on deck, he took it out as if to give it to them, then craftily he faked tripping. When the stone slipped out of his hand and into the water, a Heavenly voice proclaimed, "You gave up a material diamond for My honor, and you will receive a spiritual diamond in its place!"

While Rashi's mother was pregnant with him, she was walking in the narrow street of the Jewish quarter when a nobleman's carriage came hurtling toward her at high speed. In desperation, she pressed against the wall, which miraculously contracted, making an indentation for her to back into.

Toward the end of Rashi's life, Crusaders embarked on their conquest of the Holy Land. Godfrey of Bouillon, one of the Crusader leaders, had heard of Rashi's greatness, and asked him whether his crusade would be successful. Reluctantly, Rashi told Godfrey that he would indeed conquer Jerusalem but rule over it a very short time, and eventually return to Troyes with only three horsemen. Incensed, Godfrey told Rashi that if he returned with four riders, he would kill all the Jews of France.

Events transpired exactly as Rashi had foretold. Godfrey captured Jerusalem, but ruled it very briefly, and was driven from Eretz Israel.Arriving at the gate of Troyes, he realized that he had four horsemen. Gleefully anticipating his revenge upon Rashi, Godfrey entered the city. As the fourth rider came under the gate, a massive stone fell from the archway, killing him and his horse. Filled with awe, Godfrey arrived at the Jewish quarter, only to be told that Rashi had passed away.

Separating fact from legend, Rashi was born in 1040 in Troyes, France, and studied under the great scholars of both his hometown and Worms, Germany. His major teacher was Rabbi Jacob bar Yakar, whom Rashi quotes on numerous occasions in his commentary on the Talmud. Rashi's father, also a scholar of note, is also quoted by his illustrious son. Upon returning to his hometown at age 25, Rashi was already recognized as a major scholar. Refusing to support himself through the rabbinate, Rashi went into the wine business, while simultaneously opening a yeshiva that attracted the best minds of the Ashkenazic world. His three daughters, Miriam, Rachel, and Yocheved, married great Torah scholars, and their sons were among the great Ashkenazic Torah sages known as the Baalei HaTosafos. Rashi died in 1105, at the age of 65. In Worms, Germany, the small synagogue in which Rashi studied and taught was carefully preserved for hundreds of years, until the Nazis destroyed it.

Rashi’s commentary on Chumash, the Five Books of Moses, was immediately accepted as authoritative by all Jews, both Sephardic and Ashkenazic, during the author's lifetime, usually not the case for Torah works. It remains the premier commentary on the Chumash – so much so that it is simply unthinkable to study Chumash without Rashi. Indeed, from a young age every Jew is introduced to Rashi's unique blend of interpretations, Midrashim, laws, insights, and grammatical rules. As such, both the Torah’s personalities and commandments are viewed through Rashi’s lens. At the same time that the schoolchild studies Rashi on his level, the greatest scholars grapple with the profundity of his commentary. Indeed, hundreds of books have been written delving into the meaning of Rashi's explanations. In fact, the first Hebrew book ever printed, in 1474 CE, was a Chumash-Rashi. In addition, Rashi also wrote a commentary on Neviim and Kesuvim, which, although not as extensive as his work on Chumash, is also regarded as vital.

Along the same lines, Rashi’s commentary on the Talmud is indispensable: simply, without Rashi, the Talmud would remain a closed book to all but the most accomplished scholars. Even more so, by ensuring that every Jew would be exposed to this major repository of Torah learning, it is safe to assume that Rashi assured the spiritual survival of the Jewish people. Going line by line, Rashi's explanation of the Talmud guides the student deftly through the often-tortuous text. With uncanny ability, Rashi anticipates how the lack of seeming clarity concerns a student each step of the way; often, with a single word or phrase, he sheds much valuable light on an entire topic. Simultaneously, the most accomplished scholars laboriously pore over the same words, unearthing previously unseen intricate Talmudic analyses. In the words of the Meiri: "One word of Rashi provides the answers to bundles of questions." As such, none of the thousands of commentaries written throughout Jewish history has remotely approached this skill using the same language to reach all levels of understanding.

Appearing throughout most of the Talmud, Rashi’s commentary elucidates all the tractates except for Nedarim, Nazir, and parts of Pesachim, Bava Basra, and Makkos, which were either lost or interrupted by his death. As a Frenchman, Rashi frequently used Old French words to illustrate technical words or concepts. Other languages, such as German and Arabic, also appear in his commentary. Finally, Rashi's humility also shines forth in his writings; he is never ashamed to say that he doesn't understand the meaning or source of something. (Rabbi Akiva Eiger, for example, points out more than 40 places in the Talmud where Rashi states that he does not know something.)

Aside from his commentaries, Rashi also wrote responsaand composed piyutim. He also created the introductory piece to the selichos of Erev Rosh HaShanah (selichah 23). Near the end of his life, the ravages of the Crusades struck the Jews, and some of Rashi's writings reflect the travails of those times. Interestingly, many Ashkenazic Jews trace their lineage to Rashi, and through him to the Tanna Rabbi Jochanan HaSandlar and even King David.

Rabbi Shmuel Ben Meir (Rashbam): (11th-12th Centuries, Ashkenazic)

A grandson of Rashi and one of his premier disciples, Rashbam completed Rashi's commentary on two Talmudic tractates — the 10th chapter of Pesachim and the final 148 pages of Bava Basra. This commentary, which appears on the Talmudic page in place of Rashi, is considerably longer than that of Rashi. For example, on Bava Basra 29a, Rashi uses two words to comment on a phrase of Gemara, while Rashbam takes up four lines. Rashbam also wrote a commentary on Chumash, which adheres closely to the literal text. There, he writes that although the sages of the Mishnah and Talmud derived many teachings embedded in the verses of the Chumash, allbased on various rules of interpretation, nevertheless each passage must also be understood according to its plain meaning.

Known for his great piety, as Rashbam walked the streets he focused his eyes downward so as not to see anything improper. Once, he was about to enter a wagon, not noticing that it was being pulled by a mule and a horse, an act forbidden by the Torah. Fortunately, his brother walked by and notified him just in time. As a scholar, the Rashbam appears several times in the Tosafos commentary on the Talmud, although not as frequently as the better known Tosafists.

Rabbi Jacob Ben Meir (Rabbeinu Tam): (12th Century, Ashkenazic)

A younger brother of Rashbam, he became known as Rabbeinu Tam based on a verse (Genesis 25:27) that describes Jacob as Tam, perfect. The main founder of the Tosafist school, whose method of study became the basis of all advanced Talmudic learning for the past 900 years, Rabbeinu Tam specialized in comparing and contrasting seemingly contradictory Talmudic texts and resolving them by painstakingly unearthing the halachic principles underpinning each. Frequently, Rabbeinu Tam disagrees with Rashi's interpretation of a Talmudic discussion, with the best known of these disputes regarding the placement of the parshiyos (Scriptural verses written on small parchment rolls) in the tefillin pair. Current practice is to wear Rashi's tefillin, although many people don Rabbeinu Tam's tefillin as well. Considered the greatest Talmudist of his generation, Rabbeinu Tam was judged even greater than Rambam in scholarship.

As a leader, Rabbeinu Tam also enacted decrees affecting Jewish life.In response to the horrific blood libel in the city of Blois on 20 Sivan 1171, he decreed that day to be a public fast. Currently, although fasting is not required on 20 Sivan, pious individuals do fast and recite a special prayer service. Rabbeinu Tam also ordained that once a get has been given to a woman, under penalty of cherem no one may question its validity. Perhaps the most well-known of Rabbeinu Tam’s halachic opinions is that nightfall does not commence until 72 minutes after sunset.

He, too, experienced the horrific fury of the Crusades. In 1146, a mob entered Rabbeinu Tam’s home, robbing his possessions and wounding him grievously. In mortal danger, Rabbeinu Tam’s life was spared due to the entreaties of a nobleman, who promised the attackers that he would convert Rabbeinu Tam to Christianity. (The nobleman did not fulfill his promise.) When Rabbeinu Tam died, the sense of communal loss was so great that one of his students, a Kohen, stated that had he been present at the funeral, he would have allowed himself to become tamei (ritually impure) through contact with the coffin, an act normally forbidden to a Kohen. (There are instances where such an action is permitted, however.)

Baalei Tosafos: (12th 13th Centuries, Ashkenazic)

Tosafos (additions) is the name given to notes of scholarly analysis on the logic of the Talmud and Rashi's explanation of it; the scholars involved in this form of learning are known as the Baalei Tosafos. These sages, largely centered in the Ashkenazic strongholds of Northern France and Germany, were also found in England, Austria, and Central Europe (corresponding to the present-day Czech Republic). A Tosafos is usually written in question and answer form, much in the manner of the Talmud itself, attempting to resolve contradictions between Talmudic tractates, problems in Talmudic logic, and difficulties with Rashi's understanding of a topic. On some occasions, Tosafos will clarify an unfamiliar subject, or if two Talmudic sages possess the same name will identify the particular scholar. Occasionally, Tosafos will rule on halachic issues.

Many collections of Tosafos exist, and it is unclear why the Tosafos found in current editions of the Talmud were printed while others were not, especially since not all tractates possess Tosafos from the same author. Major Tosafists included Rabbeinu Tam, Rabbi Yitzchak HaZaken (known as the Ri), Rabbi Yitzchak ben Asher (the Riva), Rabbi Judah ben Nassan (Rivan), Rabbi Yitzchak ben Meir (Rivam), and Rabbi Eliezer of Touques. A number of Tosafists were sons-in-law and grandsons of Rashi. For Talmudic analysis, studying Tosafos is essential; otherwise, one's understanding of the Talmudic topic is superficial – and suspect. Not uniform, Tosafos' comments on a subject can run from one word to two sides of a page. On one occasion, at the end of a discussion taking up a full side, Tosafos remarks, "Let's not dwell too long on this topic."

Rabbi Meir of Rothenberg: (13th Century, Ashkenazic)

Regarded as the leading Ashkenazic halachic authority of his generation, when Rabbi Meir attempted to flee oppression in Germany, he was caught by the emperor's agents and imprisoned. When the emperor demanded a huge ransom from the Jewish community for his release, they were willing to pay, but Rabbi Meir refused to consider the proposal. Despite the loss to the community of his leadership, and weakening his Torah study, Rabbi Meir feared that such ransoms would set a bad precedent: any time an unjust ruler needed money he could kidnap a leading Torah authority. Although his students were permitted to visit him and study, heroically Rabbi Meir remained in prison for the last seven years of his life. Afterward, the vengeful emperor kept Rabbi Meir's remains in prison another 14 years, perhaps the only instance in history of someone remaining incarcerated after his death. Finally, a wealthy Jew named Alexander Vimpen redeemed the body for a great sum, asking only that he be eventually buried near the great rav, a request that was honored. As a result of Rabbi Meir's self-sacrifice, the government no longer captured great sages for ransom. In addition, Rabbi Meir played a major role in the development of current halacha. His major disciple, the Rosh, is one of the three authorities on which the Shulchan Aruch is based. Rabbi Meir's numerous Shaalos Uteshuvos are also considered authoritative.

Rabbi Asher Ben Yechiel (Rosh): (13th-14th Centuries, Ashkenazic)

Along with the Rif and Rambam, Rabbi Asher, known as the Rosh,is one of the three pillars of halacha. Born in Germany, he assumed leadership of Ashkenazic Jewry at a time of terrible persecution. Fearing a fate similar to Rabbi Meir of Rothenberg, Rosh fled to Spain, settling in Toledo and becoming the leader of Spanish Jewry. Of all the Rishonim, Rosh stands unique in becoming the recognized leader of both strains of the Jewish people. While in Toledo, Rosh established a yeshiva that introduced the Ashkenazic method of the Tosafists to the Sephardim.

Rabbi Asher's most famous work, the halachic digest compiled on many Talmudic tractates, is printed at the end of each tractate. A masterful analysis of both Sephardic and Ashkenazic authorities on each topic, Rosh appended the conclusion he felt was correct. Due to its impartial recording of all opinions, the commentary won wide acceptance, and is regarded as indispensable to the understanding of how halacha evolves from the Talmud.

Another of Rosh's masterpieces, Orchos Chaim L'Rosh, is a guidebook to ethical living. Containing both practical and moral advice — such as don't act in a rush, ask forgiveness for reciting the benediction of Selach Lanu (a prayer requesting forgiveness) without concentration, and don't attempt to reason with a crazy person, because your words will be ridiculed — in many yeshivas a set portion of Orchos Chaim L'Rosh is recited daily during the month of Elul as preparation for Rosh HaShanah and Yom Kippur.

Rabbi Jacob Ben Asher: (13th-14th Centuries, Ashkenazic)

A son of Rosh, he is known as Baal HaTurim after the name of his most famous commentary. Rabbi Jacob collected the great mass of halachic opinions, both Sephardic and Ashkenazic, and rearranged it according to topic. Titling the massive work Arbaah Turim, or Four Rows, after the four rows of precious jewels that adorned one of the Kohen Gadol's priestly garments (Exodus 28:17), it was popularly known as the Tur. Divided into four sections, Orach Chaim is on the laws of prayer, the Sabbath, and the holidays; Yoreh Deah contains the laws of kashrus, family purity, mourning, and miscellaneous halachos; Even HaEzer discusses marriage, divorce, and other related issues; and Choshen Mishpat deals with monetary laws and judicial procedure. Containing more than 1,600 chapters, along with commentaries, the Tur runs to 10 folio-sized volumes. Discussing all opinions on a topic in a systematic progression, culminating with Rabbi Jacob's own opinion, due to its diversity and layout the Tur won quick acceptance and became the basis for the later Shulchan Aruch, closely patterned on the Tur. Rabbi Jacob also wrote a commentary on Chumash that has remained very popular as well.

Rabbi Israel Isserlein: (14th-15th Centuries, Ashkenazic)

Living in the 10th and last generation of the Rishonim, Rabbi Israel Isserlein’s treatise, Terumas HaDeshen, is considered a vital halachic work.

Overall, it is remarkable, when studying the origins of contemporary halacha, to note how many great Rishonim made vital contributions to its development. By the year 1500, Jews instinctively realized that an era had passed, and that all subsequent scholars would be vastly inferior to the great Rishonim.