The 33rd day of the Omer is a day of festivity and rejoicing in honor of the saintly Tanna, Rabbi Shimon bar Yochai. There are indeed sources for this among the Poskim. We are therefore customarily more joyous than usual on this day and we do not recite Tachanun (supplication prayers). This year, 5775, Lag Ba’Omer falls out this coming Thursday, beginning from Wednesday night.
Most people commonly refer to Lag Ba’Omer as being the day that Rabbi Shimon bar Yochai passed on. However, Hagaon Sho’el U’Meshiv expressed wonder about this, for if so, we should not be joyful at all as one does not rejoice about the demise of the righteous! Nevertheless, the Responsa Shem Aryeh writes that the reason why we rejoice on this day is because of what the Gemara in Masechet Shabbat (33b) writes that the evil kingdom had decreed death upon Rabbi Shimon bar Yochai and a miracle occurred and hid in a cave and was saved from certain death by the hands of the wicked Romans. We must therefore celebrate joyously on the day he departed from this world in a natural way in order to give thanks for the miracle that happened to him.
Regarding the actual idea that Rabbi Shimon bar Yochai passed away on Lag Ba’Omer, Maran Ha’Chida writes that it is incorrect that Rabbi Shimon passed away on this day and whoever says so is mistaken. He proves this from the teachings of Hagaon Rabbeinu Shmuel Vital who writes lengthily about the deep secrets of the Omer period and especially Lag Ba’Omer and he does not mention once that this day is the anniversary of Rabbi Shimon bar Yochai’s passing. He therefore writes that the reason for the joy and celebration on this day is possibly because Rabbi Akiva began teaching his five pupils who rejuvenated the world by disseminating their Torah all over the world and this spring indeed gave us life until this very day. Similarly, Hagaon Peri Chadash writes that the primary reason for rejoicing on this day is because of the students of Rabbi Akiva who stayed alive and spread Torah to the entire world. Since from this day on these students stayed among the living, we therefore hold festivities on this day.
Some customarily visit the grave of Rabbi Shimon bar Yochai on the day of Lag Ba’Omer and to pray and read as much Tehillim as they can there. However, every individual must think deeply before performing any action to see if it will indeed be worthy before Hashem. Thus, before one decides to visit the graves of the righteous on Lag Ba’Omer, one must evaluate whether this is indeed worthwhile in all aspects.
The Sefer Sedeh Chemed writes that on the day of Lag Ba’Omer, the secrets of the Torah were revealed by Rabbi Shimon bar Yochai. This was also the day that Rabbi Shimon received Semicha (ordination). It is for this reason that we rejoice on this day. He writes that the Torah scholars in Teveria in his generation wrote likewise.
Rabbeinu Chaim Vital (principle pupil of the holy Ari z”l) writes: “I have seen my master, the Ari z”l, visit the graves of Rabbi Shimon bar Yochai and his son Rabbi Elazar on the day of Lag Ba’Omer. He and his entire family stayed there for three days. This was during the first time that he arrived from Egypt (the Ari z”l lost his father at a young age and he and his mother went to live with his uncle in Egypt). However, I do not know if at that point he was an expert in the tremendous wisdom he gleaned afterwards. Rabbi Yonatan Sagis has told me that before I had gone to learn by my master, Rabbeinu Ha’Ari z”l took his young son there along with his entire family and it was there that he shaved his son’s head in accordance with the known custom. He made there a day of joy and feasting. I have written all of this in order to show that there is a source for the aforementioned custom.”
Hagaon Harav Yonah Navon zt”l (rabbi of Maran Ha’Chida) writes that the custom in the holy city of Jerusalem has become to hold joyous festivities when a child receives his first haircut because of the Mitzvah of not cutting the hair on the side of the head (side locks) completely and by doing so, the Mitzvah of “Do not round off the corners of your head” is fulfilled.