Lag B’Omer is the thirty-third day of “counting the omer” – a custom in ancient Israel that began on the second day of Passover (the official advent of the grain harvest) and ended with the holiday of Shavuot.
On the second day of the Hebrew month of Nissan, farmers reaped a symbolic sheaf of barley and presented a measure of flour called an omer as an offering in the Temple. This offering marked the beginning of the seven-week period of counting the omer (also known as sefira, or “counting”).
For obscure reasons, rabbinic tradition dictates that the sefira is a time of mourning. The most common explanation lies in a Talmudic passage indicating that Rabbi Akiba’s disciples died of a plague during this period in the second century of the Common Era. Throughout the centuries, the notion of the sefira as a time of sorrow was reinforced by various persecutions and disasters that befell the Jewish people during that period.
Among Orthodox Jews, certain activities such as getting married, cutting the hair, and attending public concerts are prohibited during the forty-nine days. However, these prohibitions are lifted on the thirty-third day, Lag B’Omer. (The numerical value of the Hebrew consonant lamed [l] is thirty, and gimmel [g] is three; hence, the word lag means thirty-three, and Lag B’Omer is the thirty-third day of the omer.) The most common explanation for the lifting of the prohibitions is that the plague that killed Rabbi Akiba’s disciples ended on the thirty-third day of the omer.
Humanistic Jews reject the idea that the period between Passover and Shavuot is a period of gloom and mourning. If they observe Lag B’Omer, it is as a celebration of spring. Some Humanistic communities have picnics or hold planting ceremonies. In Israel, it is common to mark Lag B’Omer by dancing around bonfires.