From the second night of Pesach (Passover) to Shavuot, the next festival, there are exactly fifty days, seven full weeks linked by a ritual called S’firat ha-Omer, Counting the Omer (named for an offering brought to the priests as the Temple in Jerusalem at this time of year). In a sense, then, Pesach is not only a festival itself but the first part of a lengthy observance that runs through Shavuot, a progression from the liberation from Egypt through the revelation at Sinai. For that reason alone, the Omer period has importance.
Beginning on the second night of Pesach during the ma’ariv—evening service—the leader will rise and announce that she is “prepared to perform the positive commandment concerning the counting of the Omer.” She then recites the blessing for counting the Omer and announces the day and the number of weeks and days thus far elapsed.
In the times of the Temple, Jews were instructed to bring a small harvest offering of grain to the priests on the second day of Pesach, called the Omer offering. From that day, as instructed in Leviticus 23: 9, “you shall count seven weeks,” up to Shavuot. The Temple is long since gone, and for the most part Jews have ceased to live on farmland. But still we count the Omer according to a prescribed ritual. Why?
Maimonides, one of the greatest of Jewish sages, says that the reason for counting the Omer is to express the eagerness of the Jewish people, freed from bondage in Egypt, to receive the Torah at Sinai, an eagerness that we want to relive. More than that, the Omer period serves as a bridge between the celebration of freedom at Pesach and the celebration of law at Shavuot, a link between two concepts that Jewish thought sees as essential to on another.
For historical reasons that are at best uncertain (but probably having to do with a plague that, coinciding with the Omer period, struck and killed 24,000 students of Rabbi Akiba’s during the Bar Kokhba revolt against Rome in the 130s C.E.), this is considered a period of semi-mourning and sadness. Traditionally observant Jews will not get their hair cut or shave; marriages are not held during this seven-week period, and public festivities are avoided. (Although no one actually mourns for the entire Omer period—Jews observe either the period from the second night of Passover until Lag b’Omer or from Rosh Chodesh—the new month—Sivan until Shavuot—marriages are not held in respect for both customs).
However, there is one day of respite from the mournful Omer period, the thirty-third day of the counting, Lag b’Omer. Lag b’Omer is a minor holiday of obscure origins, celebrated with picnics and bonfires. There are several rather unsatisfying explanations for its existence; the one most often cited states that the plague that afflicted Akiva’s students lifted on this day. In Israel the holiday is particularly identified with the great mystic Simeon Bar Yokhai (second century C.E.), allegedly marking the day of his death; Hasids and Sephardim travel to Meron, his birthplace. If they have three-year-old sons, they will give them their first haircuts at Meron on this day.
Reprinted with permission of the author from Essential Judaism: A Complete Guide to Beliefs, Customs, and Rituals by George Robinson. Pocket Books.