Shavu’os is when we received the Torah, and it is a very special day. There is a minhag to treat Shavu’os night very specially. The Arizal said (and is so quoted in the Ba’er Heitev commentary on the Shulchan Aruch) that someone who stays up learning all night on Shavu’os is guaranteed that he will not be harmed all year long. This shows that a person’s very life depends on what he does this night, because this is when we received the Torah.
It is surely a very important thing to learn Torah on the day the Torah was given. And many people learn with great energy and excitement. This itself is a very important thing. But it seems that the awesomeness of Shavu’os actually stems from a different point, which Chazal say is the central point of the holiday. Practically speaking, whether a person attains lofty spiritual levels or misses out on them depends on this point.
Said R. Elazar: According to all views, on Shavu’os we also need לכם. What is the reason? It is the day the Torah was given.
There is a disagreement among the Tanna’im regarding other holidays, whether there is an obligation to have a festive Yom Tov meal or not. One view holds that a person may make the day כולו לה’, devoted solely to spiritual matters, to Torah learning and tefilah, and there is no need to have a se’udah. But on Shavu’os, everyone agrees that besides the spiritual avodah of the day, there is also a mitzvah to have a festive Yom Tov meal. Why? Because on this day we received the Torah.
The same section of Gemara continues as follows:
Rav Yosef would say on Shavu’os, “Cook for me a choice calf!” He would explain, “If not for what this day did for me, there are lots of ‘Yosefs’ in the street.”
