Shavuot, the feast of weeks, is celebrated seven weeks after the second Passover seder. Although Shavuot began as an ancient grain harvest festival, the holiday has been identified since biblical times with the giving of the Torah on Mount Sinai.
The word Shavuot means "weeks", and it marks the conclusion of the Counting of the Omer. Its date is directly linked to that of Passover; the Torah mandates the seven-week Counting of the Omer, beginning on the second day of Passover, to be immediately followed by Shavuot. This counting of days and weeks is understood to express anticipation and desire for the giving of the Torah. On Passover, the people of Israel were freed from their enslavement to Pharaoh; on Shavuot, they were given the Torah and became a nation committed to serving God.
One of the biblically ordained Three Pilgrimage Festivals, Shavuot is traditionally celebrated in the Land of Israel for one day and for two days in the Diaspora. While there is more awareness of the festival in Israel among secular Jews, generally Shavuot is widely ignored by non-practicing Jews.
The practice of staying up all Shavuot night to study Torah – known as Tiqun Leyl Shavuot – is linked to a Midrash which relates that the night before the Torah was given, the Israelites retired early to be well-rested for the momentous day ahead. They overslept and Moses had to wake them up because God was already waiting on the mountaintop. To rectify this perceived flaw in the national character, many religious Jews stay up all night to learn Torah.
Any subject may be studied on Shavuot night, although Talmud, Mishnah, and Torah typically top the list. People may learn alone or with a chavruta (study partner), or attend late-night shiurim (lectures) and study groups. In keeping with the custom of engaging in all-night Torah study, leading 16th century kabbalist Isaac Luria arranged a recital consisting of excerpts from the beginning and end of each of the 24 books of Tanakh (including the reading in full of several key sections such as the account of the days of creation, the Exodus, the giving of the Ten Commandments and the Shema) and the 63 tractates of Mishnah, followed by the reading of Sefer Yetzirah, the 613 commandments as enumerated by Maimonides, and excerpts from the Zohar, with opening and concluding prayers. The whole reading is divided into thirteen parts, after each of which a Kaddish d-Rabbanan is recited when the Tiqun is studied with a minyan. Today, this service is held in many communities, with the notable exception of Spanish and Portuguese Jews. The service is printed in a book called Tiqun Leyl Shavuot. There exist similar books for the vigils before the seventh day of Pesach and Hosha'ana Rabbah.