Omer

Counting of the Omer (or Sefirat Ha'omer, Hebrew: ספירת העומר) is a verbal counting of each of the forty-nine days between the Jewish holidays of Passover and Shavuot. This mitzvah derives from the Torah commandment to count forty-nine days beginning from the day on which the Omer, a sacrifice containing an omer-measure of barley, was offered in the Temple in Jerusalem, up until the day before an offering of wheat was brought to the Temple on Shavuot. The Counting of the Omer begins on the second day of Passover and ends the day before the holiday of Shavuot. The idea of counting each day represents spiritual preparation and anticipation for the giving of the Torah, which was given by G-d on Mount Sinai on the fiftieth day, Shavuot. The Sefer HaChinuch states that the Jewish people were only freed from Egypt at Passover in order to receive the Torah at Shavuot and to fulfill its laws. Thus the Counting of the Omer demonstrates how much a Jew desires to accept the Torah in his own life. The omer is a Biblical measure of volume of grain. On the second day of Passover, an omer of barley was offered in the Temple, signalling the allowance of the consumption of chadash (grains from the new harvest). On the 50th day after the beginning of the count, corresponding to the holiday of Shavuot, two loaves made of wheat were offered in the Temple to signal the start of the wheat harvest. In keeping with the themes of spiritual growth and character development during this period, the Jewish sages compare the process of growth to the two types of grain offered at either pole of the counting period. In ancient times, barley was an animal food and wheat, a human food. At Passover, the Jews were raised out of the Egyptian exile although they had sunken almost to the point of no return. The Exodus was unearned, a gift from G-d, like the food of animals who are not expected to develop their spiritual potential. For the next forty-nine days, however, the Jewish people worked on themselves to be able to receive the Torah on their own merit. The receiving of the Torah required spiritual elevation and active cooperation. Thus the Shavuot offering is "people food".
The period of Omer is considered to be a time of potential for inner growth - for a person to work on one's middot or good characteristics through reflection and development of one aspect each day for the 49 days of the counting. So the Omer is an in-between time. “You shall count 50 days to the day after the seventh Sabbath; then you shall present a new grain offering to the L-rd.” “On the morrow after the Sabbath” following Passover, as the first fruits of the barley harvest were being offered in the Temple, Messiah was ‘raised from the dead, the first fruits of those who are asleep (1 Cor. 15:20). The festival of First Fruits was the ‘morrow after the Sabbath’, on Sunday. The celebration was to be over G-d’s replanting of the earth in the spring. Celebrating the resurrection of the L-rd was on First Fruits. First Fruits was the last of the feasts that the L-rd was seen personally fulfilling on earth.