[1] According to some of the Rishonim, it is the day on which the plague that killed Rabbi Akiva's 24,000 disciples came to an end, and for this reason the mourning period of the Counting of the Omer concludes on Lag BaOmer in many communities.

The earliest clear reference to the observance of Lag BaOmer is a gloss to Mahzor Vitry in BL Add MS 27,201 (f. 227v), if it is the work of Isaac ben Dorbolo.

After the Muslim conquest and the end of Christian oppression of Jews in Israel, mourning practices ceased to be observed.

[17] Another theory posits that the connection between Lag Baomer and Shimon Bar Yochai arose from a general pilgrimage to Mount Meron on Pesach Sheini (15th of Iyar), specifically to Hillel's cave wherein water filled up the cave's cisterns and sometimes overflowed; the natural phenomenon poorly understood then was considered miraculous and attracted Jews and Muslims alike.

[18] Lag BaOmer has another significance based on the Kabbalistic custom of assigning a Sefirah to each day and week of the Omer count.

[26] For many years, New York based Rabbi Aaron Teitelbaum of Satmar discouraged bonfires, saying it was not the custom to light them outside of the Land of Israel.

[27] However, when his father Rabbi Moses Teitelbaum instructed him to organize a large bonfire in the Satmar enclave of Kiryas Joel tens of thousands turned up.

[28] For Zionists (see section below), the bonfires are said to represent the signal fires that the Bar Kokhba rebels lit on the mountaintops to relay messages,[29] or are in remembrance of the Bar Kokhba revolt against the Romans, who had forbidden the kindling of fires that signalled the start of Jewish holidays.

[30] Historically, children across Israel used to go out and play with bows and arrows, reflecting the Midrashic statement that the rainbow (the sign of God's promise to never again destroy the earth with a flood; Genesis 9:11–13) was not seen during Bar Yochai's lifetime, as his merit protected the world.

It is also marked in the Israel Defense Forces as a week of the Gadna program (youth brigades) which were established on Lag BaOmer in 1941[dubious – discuss] and which bear the emblem of a bow and arrow.

[33] Several traditional songs are associated with the holiday; these are sung around bonfires, at weddings, and at tishen held by Hasidic Rebbes on Lag BaOmer.

[34][35] Other songs include "Ve'Amartem Koh LeChai", a poem arranged as an alphabetical acrostic, and "Amar Rabbi Akiva".

Teachings of Rabbi Shimon Bar Yochai, both from the Talmud and the Zohar, are generally expounded upon by Rebbes at their tishen.

[citation needed] Some rabbis, namely Moses Sofer[37] and Joseph Saul Nathansohn,[38] have opposed the celebration of or the practice of certain customs observed on Lag BaOmer.

[citation needed] In modern Israel, early Zionists redefined Lag BaOmer from a rabbinic-oriented celebration to a commemoration of the Bar Kokhba revolt against the Roman Empire (132–136 CE).

According to work published by Yael Zerubavel of Rutgers University, a number of Lag BaOmer traditions were reinterpreted by Zionist ideologues to focus on the victory of the Bar Kokhba rebels rather than their ultimate defeat at Betar three years later.

As Benjamin Lau writes in Haaretz: This is how Lag Ba'omer became a part of the Israeli-Zionist psyche during the first years of Zionism and Israel.

A clear distinction became evident between Jews and Israelis in the way the day was celebrated: The religious Jews lit torches in Rashbi's [Shimon bar Yochai's] honor and sang songs about him, while young Israelis, sitting around an alternative bonfire, sang about a hero "whom the entire nation loved" and focused on the image of a powerful hero who galloped on a lion in his charges against the Romans.