An Offering
According to the Bible (Leviticus 23:11), an offering, consisting of an omer (a specific measure) of barley, was brought to the Temple on the second day of Pesach. The omer was, in fact, a yield of a sheaf of barley. Until that offering was made, the Bible records, "you shall eat no bread or parched grain or fresh ears."

Counting
From that day onwards, it was necessary to count forty nine days until Shavuot - the Feast of the Wheat Harvest. After the destruction of the Temple, the practice of bringing barley was discontinued but Jews continued to "count the omer period," a custom which has continued throughout the ages.

Weathering it
The Omer period has several interesting angles: In the agricultural world, it represented a period of tremendous tension for the Judean farmer who was two Jewish holidays of Pesach and Shavuot. Indeed, the Hebrew word for a hot dry wind, chamsin, derives its source from the Arabic word for fifty, since this bothersome weather occurred so frequently during this period.The hot dry wind could burn the stalks of the ripening wheat, thus spoiling the produce and threatening the farmer's sustenance.

Reminder of the Source
In Jewish thought and tradition, the optimal proportions of rains (and wind and sun) were to be a reward for keeping God's commandments. So, the counting of the days of the Omer reminded the farmer of the source of his success in producing grain and olives and grapes - the three staple crops recorded in the Bible. The daily omer count consequently offered an emotional and practical spur to the landowner to be more faithful to the ongoing demands of his spiritual duties.

Anticipation
The tension increased as the days passed, but so did the anticipation of going up to the Temple on the upcoming festival of Shavuot. Shavuot was the religious climax of the counting period. Since Shavuot also commemorated the Giving of the Torah on Mt. Sinai, observance of the holiday continued even in the post-Temple period when the offerings were discontinued. The period of the Omer thus became the natural bridge between Pesach and Shavuot. For what reason did the Children of Israel leave Egypt if not to receive the Torah? Thus the Jew counted the Omer as a bride and groom would count the days to their marriage: as each day passes the anticipation grows.

An Ascent
The Kabbalists had a different interpretation of the Omer based on the various permutations (7 x 7) of the Sefirot or mystical emanations. These Sefirot denote the ascent out of the 49 "gates" of impurity of the Egyptian bondage to the purity of the revelation at Sinai. In many prayer books and Omer counting charts, these combinations are listed at the side of each day recorded.

A Mourning Period
Through the years, the Omer period has become identified with sad memories for Jewry. Massacres occurred during the period of the Romans and later still during the Crusades. In the days of the Roman Emperor Hadrian, the Jews - led by Bar Kokhba - attempted to drive out the foreign oppressors from Judea. The revolt was unsuccessful and during the fighting thousands of Jews lost their lives.

According to tradition, numerous students of Rabbi Akiva died as a result of a plague that raged during the days of the Omer counting. For that reason, it is customary to observe a a period of semi-mourning during this period, most prominently during the whole Hebrew month of Iyar, when weddings are not held, hair is not cut, and music is not heard. On one day only, the 18th Iyar and the thirty-third day of the Omer - in Hebrew: Lag B'Omer, after the acronym for the number 33 - this ban is lifted, since the plague is said to have ceased on that day.