"On the seventh day, you shall have a holy day." (Vayikra 23:8)
We are commanded to refrain from all work (with the exception of food
preparation) on the seventh day of Pesach (and the eighth in chutz
68: Resting on Shavuos
"In the midst of that day [Shavuos], you shall have a holy day."
It is a mitzvah to celebrate the holiday of Shavuos, which is fifty days
after Pesach. This day is called "zeman matan Toraseinu," the day of the
giving of our Torah. The world exists only due to the Jewish people's
acceptance of the Torah. Once a year, on Shavuos, we renew our commitment
to receiving the Torah. It is customary to stay up all night learning in
order to demonstrate our love and eagerness for Torah.