Although the sages had removed themselves from overt participation in the government, they realized that due to Roman meddling in the Sanhedrin the spiritual life of the nation was being compromised. As such, the sages decided that they, rather than the Sanhedrin, should appoint the Nasi. Hillel, born in Babylon and a maternal scion of the House of David, was proclaimed Nasi in 3728, a position that included the right to pass on the title to his descendants. Indeed, the House of Hillel produced 14 generations of great leaders, spanning nearly 400 years, and guiding the Jewish people through some of their most difficult times.

Hillel and his Torah colleague Shammai were both disciples of Shemaya and Avtalyon as well as the last of the Zugos. (The five generations of Zugos were Jose ben Joezer and Jose ben Jochanan, Joshua ben Perachiah and Nitai HaArbeli, Judah ben Tabbai and Shimon ben Shatach, Shemaya and Avtalyon, and Hillel and Shammai.) Hillel and Shammai were revered by the Jewish people, so much so that even the evil Herod feared to harm them. In addition, Hillel's devotion to Torah study was legendary. Once, unable to afford a yeshiva entrance fee, he crawled up to the skylight in order to hear the lecture and was nearly frozen to death by accumulating snow. He was also possessed of great character traits. His reputation as being impossible to anger, for example, was such that someone bet 400 dinars — a very large sum — that he could cause Hillel to lose his temper. Try as he might, the man could not anger Hillel – and so lost the bet! Hillel is also the author of the famous saying: "What is hateful to you do not do unto others.”

In terms of Jewish law, Hillel's best-known enactment is the prozbul, a document that a creditor writes before the end of shmittah assigning collection of his loans to a court. (In shmittah, the Torah cancels all private debts. Because of the chilling effect such cancellation has on commerce, and because debts to a court are never cancelled, Hillel created a mechanism to keep the Jewish economy alive.) Hillel’s partner Shammai, also a paragon of virtue, taught, "Greet every person with a cheerful face." He was also a fearless upholder of the Torah’s honor, standing up to Herod and brooking no mockery of Judaism. (The Talmud, in a famous story, contrasts the strict approach of Shammai and the gentle approach of Hillel regarding potential converts who appeared before them displaying mocking attitudes toward Judaism.)

Bais Shammai and Bais Hillel and the Proliferation of Disputes

Shammai and Hillel themselves only disagreed in three cases. However, due to increased Roman persecution, their disciples were unable to analyze new situations as deeply as Jewish scholars once could. As a result, the emerging scholars broke off into two schools of thought, known as Bais Shammai and Bais Hillel, and wound up disputing more than 300 cases. This beginning of large-scale argumentation (machlokes) is viewed by the Talmud as a sad diminution in Torah scholarship, which, due to the lack of clarity, had drastic results for the Jewish people. Although these two schools disagreed about many issues, the scholars personally treated each other with great love and respect. Because of such fine behavior, and because the scholars’ sole motivation was to understand G‑d's will as reflected in the Torah, and not to engage in personal self-aggrandizement, the Mishnah describes the disputes of Bais Shammai and Bais Hillel as "being for the sake of Heaven."

In most cases, Bais Shammai is stricter while Bais Hillel takes a more lenient approach. In addition, the Talmud rules in favor of Bais Hillel in virtually all situations. One of the more famous disputes involves the number of lights kindled on each night of Chanukah: Bais Shammai holds that eight lights are lit on the first night and one less each night afterward, while Bais Hillel is of the opinion that one light is lit the first night and one more each succeeding night.

It is fitting that Bais Shammai and Bais Hillel are called the first Tannaim, or scholars of the Mishnah. And their longevity is unmatched, for these two schools of sages spanned five generations over a period of approximately 200 years. (Although all the sages from Shimon HaTzadik on are technically considered Tannaim, due to Bais Hillel’s and Bais Shammai’s frequent appearance in the Mishnah, the term is commonly used to describe the rabbis following Shammai and Hillel themselves.)