Rabbi Moshe Chaim Luzzatto (1707 - 1746, 26 Iyar 5506), also known by the Hebrew acronym RaMHaL, was a prominent Italian Jewish rabbi, kabbalist, and philosopher. Born in Padua, he received classical Jewish and Italian educations, showing a predilection for literature at a very early age. He attended the University of Padua and with his vast knowledge in religious lore, the arts, and science, he quickly became the dominant figure in that group. His writings demonstrate mastery of the Tanach, the Talmud, and the rabbinical commentaries and codes of Jewish law. The turning point in Luzzatto's life came at the age of twenty, when he received direct instruction from a mystical being known as the Maggid. While such stories were not unknown in kabbalistic circles, it was unheard of for someone of such a young age. His peers were enthralled by his written accounts of these "Divine lessons", but the leading Italian rabbinical authorities were highly suspicious and threatened to excommunicate him, because of the similarities between Luzzatto's writings and Shabbatai Zevi's.

In 1735 Luzzatto left Italy for Amsterdam, where he was able to pursue his studies of the kabbalah relatively unhindered. Earning a living as a diamond cutter, he continued writing but refused to teach. It was in this period that he wrote what is his magnum opus the Mesillat Yesharim (1740), essentially an ethical treatise but with certain mystical underpinnings. The book presents a step-by-step process by which every person can overcome the inclination to sin and reach a level of prophecy. Another prominent work, Derekh Hashem (The Way of G-d) is a philosophical text about G-d's purpose in Creation, justice, and ethics. The same concepts are discussed in a shorter book called Maamar HaIkarim. Daat Tevunot also found its existence in the Dutch city as the missing link between rationality and Kabbalah, a dialogue between the intellect and the soul. On the other hand, Derekh Tevunoth introduces the logic which structures Talmudic debates as a means to understanding the world around us.

One major rabbinic contemporary who praised Luzzatto's writing was Rabbi Eliyahu of Vilna, the Vilna Gaon (1720 - 1797), who was considered to be the most authoritative Torah sage of the modern era as well as a great kabbalist himself. Luzzatto also wrote poetry and drama, most of it seeming secular on the surface, but many scholars have identified mystical undertones in this body of work as well. His writing is strongly influenced by the Jewish poets of Spain and by contemporary Italian authors.

Frustrated by his inability to teach kabbalah, Luzzatto left Amsterdam for the Holy Land in 1743, settling in Acre. Three years later, he and his family died in a plague. It was only a century later that Luzzato was rediscovered by the Mussar Movement, which adopted his ethical works. It was the great Torah ethicist, Rabbi Yisrael Salanter (1810 - 1883) who placed the Messilat Yesharim at the heart of the Mussar (ethics) curriculum of the major Yeshivot of Eastern Europe.

Rabbi Yisroel Lipkin, better known as "Rav Yisroel Salanter" or "Israel Salanter" (1810 - 1883), was a famed Rosh yeshiva and Talmudist and the father of the Musar movement developed in 19th century Orthodox Eastern Europe, particularly among the Lithuanian Jews. The epithet Salanter was added to his name due since most of his schooling took place in Salant, where he came under the influence of Rabbi Yosef Zundel of Salant. Rabbi Lipkin was born in Zagare, Lithuania on November 3, 1810, the son of Rabbi Zev Wolf, the Rabbi of that town and later Av Beth Din of Goldingen and Telz. As a boy, he studied with Rabbi Tzvi Hirsh Braude of Salant. In 1823, Rabbi Lipkin settled in Salant, where he continued his studies under Rabbi Hirsch Broda and Rabbi Yosef Zundel of Salant, himself a disciple of Rabbi Chaim Volozhin. Rabbi Zundel exerted a deep influence on the development of Rabbi Lipkin's character, he had stressed religious self improvement (musar), which Rabbi Lipkin popularized and developed into a complete method.

He was a tremendous Torah scholar. At Rabbi Lipkin's suggestion, the Musar writings of Moshe Chaim Luzzatto, Solomon ibn Gabirol, and Menachem Mendel Lefin were reprinted and popularized in Vilna. Despite the prohibition against doing work on Shabbat Rabbi Salanter set an example for the Lithuanian Jewish community during the cholera epidemic of 1848. He made certain that any necessary relief work on Shabbat for Jews was done by Jews. Rabbi Salanter held that both Jewish ethics and law mandated that the laws of the Torah must be put aside in order to save lives. During Yom Kippur Rabbi Salanter ordered that Jews that year must not abide by the traditional fast, but instead must eat in order to maintain their health, again for emergency health reasons. Rabbi Lipkin is also known as one of the first people to try to translate the Talmud into another language. However, he died before he could finish this immense project.

Rabbi Nosson Zvi (Nota Hirsh) Finkel (1849-1927), was born in Lithuania and died in the British Mandate of Palestine. He was an influential leader of Orthodox Judaism in Eastern Europe and founder of the Slabodka Yeshiva, in the town of Slabodka. He is better known by the Yiddish appellation The Alter ("the Elder") of Slabodka. At a young age, he went to study at the Kelm Talmud Torah under Rabbi Simcha Zissel Ziv, "the Alter of Kelm." Despite his influence, he was an intensely private person. Yet, he personally oversaw the complete student body of the yeshiva. His motto was summed up in the words Gadlus HaAdam ("Greatness of Man"). He stressed the need for mussar (ethics), using works such as those of Rabbi Moshe Chaim Luzzatto, polishing the character traits of his students so that they would aspire to become gedolim ("great ones") in all areas of both scholarship, and personal ethics. He would send teams of his trained prized pupils to places that needed a boost in religious observance and learning of Torah. His own son, Eliezer Yehudah (Lazer Yudel) Finkel eventually became the head of the far older Mir yeshiva, eventually leading it all the way to Jerusalem where it is today the largest yeshiva in the world with thousands of students.

Rabbi Finkel staged one of the most dramatic moves in the history of yeshivot. In the 1920s he decided to create a branch of his yeshiva in the Land of Israel, together with the dean Rabbi Moshe Mordechai Epstein, setting it up in Hebron and sending waves of hand-picked students there, culminating with his own permanent aliyah, "going up", to the Holy Land two years before his passing. He founded his own institution in the town of Hebron called Knesset Yisroel, "Gathering of Israel", which moved to Jerusalem following the massacre of Jews during the 1929 Arab riots in Hebron in which many of the yeshiva students perished.

Many of his pupils were to become major leaders of Orthodox Judaism in the USA and Israel. Some of the more famous students are: Rabbi Eliezer Yehuda Finkel (son of the Alter) of the Mirrer Yeshiva in Mir and Jerusalem, Israel, Rabbi Yitzchok Hutner of Yeshiva Rabbi Chaim Berlin of Brooklyn, New York, Rabbi Yaakov Kamenetsky of Yeshiva Torah Vodaas in Brooklyn, New York, Rabbi Avrohom Eliyahu Kaplan of Hildesheimer Rabbinical Seminary in Berlin, Germany, Rabbi Aaron Kotler, of Beth Medrash Govoha in Lakewood, New Jersey, Rabbi Dovid Leibowitz of Yeshiva Chofetz Chaim, Rabbinical Seminary of America in Queens, New York, Rabbi Yaakov Yitzchok Ruderman of Yeshivas Ner Yisroel in Baltimore, Maryland, Rabbi Yechezkel Sarna, head of Hevron Yeshiva, Jerusalem, Israel, Rabbi Isaac Sherr, head of the Slabodka Yeshiva of Bnei Brak, Israel, Rabbi Elazar Shach of Ponevezh Yeshiva in Bnei Brak, Israel, Rabbi Yechiel Yaakov Weinberg of Hildesheimer Rabbinical Seminary in Berlin, Germany.

The Alter did not author any books or essays personally, but some of his ethical discourses were published under the name Ohr HaTzafun, "The Hidden Light", (also meaning "The Light of the Hidden (One)"). The word Ha-Tz[a]-F[u]-N also being the four initials of his name, but not in order ("Hirsh-Tzvi-Finkel-Nota"). The title alludes to the hidden and mysterious nature of its subject, as he used to sign his name as Hatzafun.