Shavuos: How Could the Bnei Yisroel Oversleep The Day of Matan Torah?
Our Minhag is to stay up all Shavuos night in order to make sure we don't oversleep on the morning of Kabalas HaTorah. Chazal tell us that on the morning of Matan Torah the Bnei Yisroel were sleeping and Moshe Rabbeinu had to wake them up and bring them to Kabalas HaTorah. How could this be? Weren't they up preparing all night for this unprecedented historic event?
Reb Chaim Yaakov Safran, the Komarna Rebbe, in the Hakdama to the Chumash Heichal HaBracha, answers as follows.
The Rambam says that there are many levels of Nevuah [prophesy]. Typically, it is an out of body experience where the Navi's neshama reaches such a high level that it leaves his body, which remains in a trance, while the neshama receives the nevuah. The Rambam calls this "sheina", sleep. In order to prepare to hear Hashem's words at Har Sinai the Bnei Yisroel brought themselves to this state of "sheina".
On the other hand, Moshe Rabbeinu who had purified his soul and body to a state of perfection, was the only Navi in history that was able to receive nevuah in a perfectly conscious state. This is called "Aspaklariya HaMeira".
This explains the midrash. Bnei Yisroel went to "sleep" or "sheina" to enable themselves to hear Hashem's words. Until, that is, Moshe Rabbeinu woke them up. He brought them up to his level of Aspaklariya HaMeira in order for the Torah to be given to humans and not angels. At Har Sinai we heard, for the only time in history, Hashem speak while we were fully conscious.