And thou shalt observe the feast of weeks, even of the first-fruits of wheat harvest, and the feast of ingathering at the turn of the year. (Exodus 34:22)
Shavuot (lit. weeks), one of Judaism’s three pilgrimage festivals (along with Passover and Sukkot), marks the giving of the Torah (the Five Books of Moses) on Mt. Sinai. The holiday is celebrated exactly seven weeks after the first day of Passover, which marks the Exodus itself.
A fundamentally agricultural holiday, Shavuot is also called the Harvest Holiday and the First Fruits Holiday (as it is referred to in Numbers 28:26 and Exodus 23:16, respectively), commemorating the custom of bringing offerings to the Holy Temple from the first fruits of the harvest (Deuteronomy 26:1-11) and the first animals born to the flocks (Numbers 28:26-31). This agricultural aspect of the holiday was retained even after the destruction of the Holy Temple: among the symbols of the holiday are the seven species with which the Land of Israel is blessed - wheat, barley, grapes, figs, pomegranates, olives and dates.
Shavuot is also connected to the Biblical Book of Ruth. Ruth was an ancestor of King David, who passed away on Shavuot. As Ruth was a convert to Judaism, she actively accepted the Torah, as did the Jewish people at Mt. Sinai. What’s more, the story depicted in the Book of Ruth takes place during the wheat harvest, around the time of Shavuot.
On the night of Shavuot, it is customary to eat dairy products. After the festive holiday meal, many observant Jews will follow a time-honored tradition of studying Torah all night long in their local synagogue. They then say the morning prayers at the earliest permitted time, symbolic of the enthusiasm of the Jewish people to receive the Torah.
The Shavuot morning prayers are marked by special hymns and scriptural readings, including the Book of Ruth. Some communities decorate their synagogues with green plants and flowers, reflecting traditions that Mt. Sinai was a green mountain and that Shavuot is a day of judgment for fruit trees.