The custom to learn Torah on the eve of Shavuot [also see here for more information]
Millions of people all over the world are eager to receive “only” one blessing from the Creator of the world. They are willing to work hard with all their heart and soul in order to merit being included in the category of fortunate people, who are listed in the sefer zichronot of Hashem. Of course, to merit receiving The ultimate blessing, with a capital “T”, is not simple. However, once a year a unique opportunity presents itself to receive not only one blessing from Hashem, but to receive a package full of blessings, with seventy blessings all together.
This unique opportunity will commence on Motzei Shabbat, on the eve of Shavuot, since on this night it is the common practice throughout the Diaspora to remain awake all night to study Torah until dawn.
What is the reward for those who learn Torah all night on the eve of Shavuot?
This is what the holy Zohar reveals [Introduction to the Zohar chelek I, p. 8]:
All those who complete the tikkun on this night and do so joyously, will be registered and recorded in the sefer zichronot, and Hakadosh Baruch Hu blesses them with seventy blessings and with crowns from the Upper world. Regarding them it says, “Then those who fear Hashem spoke to one another and Hashem listened and heard, and a book of remembrance was written before Him for those who fear Hashem and those who give thought to His Name.”
Regarding the segulah of learning Torah throughout the eve of Shavuot, the sefer on the customs of the Arizal, called Pitora d’Abba, states: All those who did not sleep in this night at all, not even for one moment, and was involved in the study of Torah the entire night, is promised that he will live out the year and no harm will befall him in that year. As Rabbi Shimon Bar Yochai writes in his introduction to Bereishit, “He will live through the year in peace.” Moreover, a person’s life is determined according to this matter, because if he will not sleep at all on the eve of Shavuot, then he will surely not die that year. This is why it became a custom for Am Yisrael to delve in Torah the entire night of Shavuot.
Moreover, it is important to note that there are many communities that are meticulous about not speaking any mundane words the entire night until after the Kedushah beginning with “Keter” (כתר) in the tefillah of Mussaf. This is a special segulah, according to the Arizal, to be saved from death defined as “karet” (כרת), since the word “karet” (כרת) contains the same letters as “Keter” (כתר)
The reason for learning Torah on the eve of Shavuot is explained in Pirkei d’Rabbi Eliezer. At the time of Matan Torah, Bnei Yisrael had slept throughout the night, since sleeping on the Atzeret is pleasant, and the night is short. Hashem had to wake them up from their sleep with thunder and lightning, which occurred prior to receiving the Torah on Har Sinai. In order to make amends, Chazal established, as befitting teshuvah, to be on duty that entire night and study the holy Torah in the way they outlined, until dawn, and hear kriat HaTorah and the Ten Commandments as if we had just received them on Har Sinai.