On Lag BaOmer, the question arises: What is the great celebration on the day of Rabbi Shimon bar Yochai’s passing all about? If Rashbi’s soul is a nitzutz of the soul of Moshe Rabbeinu, on the day of Moshe Rabbeinu’s passing, the Shulchan Aruch says it is customary to fast (580:2). Similarly, on the day of the passing of Aharon HaKohen, the first of Av, the Shulchan Aruch writes that one who wishes may fast. On the first of Nissan, the passing of Nadav and Avihu, one who wishes to fast may also fast!
We do not find such a hilula – such a celebration – for any other Tanna or Rebbe, to the extent that we do not recite Tachanun on that day. In contrast, on the passing of Moshe Rabbeinu, Miriam, and all the others, we do say Tachanun! What is the great celebration about, and why do we not say Tachanun on this day?
It is brought in the sefer Pri Eitz Chaim (Sha’ar Sefirat HaOmer, 7) that his teacher, the Arizal, went with his wife and household to the tomb of Rabbi Shimon bar Yochai and Rabbi Elazar his son in Meron on Lag Ba’Omer, and stayed there for three days. He also recounts other gedolim who’d make the pilgrimage and looked at Lag Ba’Omer as a uniquely auspicious day.
The Sefer Emunat Itecha establishes a principle: just as the Kohen Gadol, anointed with the sacred oil, transcends mourning and embodies joy in the Kodesh Hakodashim, so too Rashb'i radiates joy on his hilula. Read his words:
We have a general principle from the Ba’al Shem Tov, brought in Maor Einayim, that the Torah is eternal and applies to every time and place, in general and in particular. This aspect of the Kohen Gadol applies to the generations, even in the time of exile. This is the aspect of Rabbi Shimon bar Yochai, who was in the aspect of the Kohen Gadol among his brothers:
ָ , שׁ ֶמֶן שָׂשׂוֹן מֵחֲבֵרֶ יך ָ בַּר יוֹחָאי, נִמְשׁ ַחְתָּ אַשְׁרֶ יך – Bar Yochai, you were anointed, fortunate are you, with the oil of gladness above your fellows.” And he is in the aspect of the Kodesh Hakodashim, as it is written: ֳ דָ שׁ ִ י ם ב ּ ַ ר י ו ֹ ח ָ א י , ב ּ ק ֹ דֶ שׁ ה ַ ק – Bar Yochai, in the Holy of Holies.” This is the matter of the great joy on the day of Lag Ba’Omer, which is his hilula. Some great sages questioned the joy, for what place is there for joy at the time of his passing, when the day a rabbi dies is a day of fasting, as we see in the Mishnah and Gemara. However, it is already written in the Zohar that Lag Ba’Omer is the hilula of Rabbi Shimon bar Yochai. Some wish to say that it does not mean a hilula and joy. But it is explicitly clear that it is a day of joy from the incident brought in the intentions of the Arizal... and according to our words above, since Rabbi Shimon bar Yochai is the Kohen Gadol in the aspect of the Kodesh Hakodashim, mourning has no place with him due to his aspect, which pertains to the place of joy and happiness. He is Bar Yochai, the holy anointing oil, which is the letters of “simchat kodesh” (holy joy). The Ba’al HaTanya, may his merit protect us, wrote that the soul of Rabbi Shimon was not affected by the churban, and the Ramchal wrote that his soul is the soul of redemption.
It is brought in the Zohar that Rabbi Shimon bar Yochai died while reciting the Pasuk: ִים עַד הָעוֹלָם כִּי שׁ ָם צִוָּה ה' אֶת הַבְּרָכָה חַי – For there, Hashem commanded the blessing, life forever (Tehillim 133:3). The anointing oil, as explained, rests primarily in his beard, close to his flesh, so that it does not fall due to the movement of the beard through his speech. Regarding this idea that the oil “descends upon the beard of Aharon,” Moshe was concerned. He said: “Perhaps, Heaven forbid, I touched those drops when I dressed Aharon during the days of inauguration, and thus I misused the anointing oil!” A bat kol went forth and said: כַּשֶּׁמֶן הַטּוֹב... כְּטַל חֶרְ מוֹן – Like the precious oil... like the dew of Hermon. It compares the oil in Aharon’s beard to the dew of Hermon – just as the dew of Mount Hermon, from the mountains of Eretz Yisrael, involves no misuse, so too the anointing oil in Aharon’s beard involves no misuse. Yet Aharon was still concerned. He too said: “Perhaps, even though Moshe did not misuse it, I myself misused it, for perhaps some of the oil fell on me in a place not suitable for anointing!” A bat kol went forth and said to him: ַם יַחַד הִנֵּה מַה טּוֹב וּמַה נָּעִים שׁ ֶבֶת אַחִים ג – Behold, how good and how pleasant is the dwelling of brothers together. Meaning, both of them were equal in this matter: just as Moshe did not misuse the oil, so too Aharon did not misuse it.
In his piyyut, Rabbi Shimon Lavi comes writes:
