On the first day of the week following Passover, the cereal harvest began. The first of the grain to ripen, which was sown in winter - a time when germination is difficult , was barley. First Sheafs of Barley were waived on the third day of the Passover . The counting of the Omer began at this feasts of Firstfruits. Following this other cereals get ripened. The last cereal to ripen during the season was the wheat. The grain harvest in Palestine lasted seven weeks. It began with the barley harvest during Passover and ended with the harvesting of wheat at Pentecost. Wheat is the last cereal to ripen. Pentecost was thus the concluding festival of the grain harvest, just as the Last Great Day concluded the fruit harvest (Jewish Encyclopedia, "Pentecost")

There are three designations of the term, "firstfruits" (Hebrew: bikkurim):

It is also the anniversary of Matan Torah, the Giving of the Torah, at Mount Sinai. Given to a mob without law, it meant order out of disorder.
Rom. 5: 13 "for before the law was given, sin was in the world."
Tim 1: -11 "We also know that law is made not for the righteous but for lawbreakers and rebels, the ungodly and sinful, the unholy and irreligious; for those who kill their fathers or mothers, for murderers, for adulterers and perverts, for slave traders and liars and perjurers--and for whatever else is contrary to the sound doctrine that conforms to the glorious gospel of the blessed God, which he entrusted to me."
The Law created boundaries for selfish freedom. Law is a controlling of the freedom of speech and freedom of action which are based on self.

According to Jewish theology God revealed to Moses all of the Torah, including details of his future plans of redemption. Not only God gave Moses the written law, He also gave the unwritten law - the spirit of the Law. This Oral Torah (Torah she-be-al peh) is the wisdom of the ages. They were transmitted faithfully from master to disciple as the authoritative companion to the Written Torah (Torah she-be-khtav). Eventually however, Jewish people became so legalistic that they missed the entire spiritual dimension. When Jesus confronted the Jewish teachers, this was the contention.

The Hebrew number 50 symbolically represents liberty, freedom and deliverance. Law therefore was the first step to freedom. Bible defines freedom with responsibility. The Law becomes unnecessary as responsibility grows. Karl Marx had that in vision when he said that "The State will wither away", when socialism progresses to communism. It did not because it had no provision for overcoming sin and selfishness. Socialism went from law to dictatorship. Any attempt to deal with lawlessness without dealing with sin is simply bound to failure. Over and over again historical experiments in socialism therefore failed. Sin has to be first dealt with. Israel being redeemed at Passover received the Law seven weeks later at Mount Sinai. Now they have become a nation under God - under the law.

50 represents liberty, freedom and deliverance. In the next dimension it is the jubilee - (7 x 7 + 1). Jubilee year was the year when everyone returned to their inheritance. This was the year of pardon and grace when debts are wiped out. It is the sabbath for all including the land. (Leviticus 25:8-17) This is the day of atonement.

Seven weeks after the death and resurrection of Jesus sent on the day of the Pentecost the Holy Spirit was send giving the law in the hearts of the people. If god gave Moses the law written on tablets of stones, on that day it was given written in the hearts. This is the constant presence of the Holy Spirit which shows the law - not in legalism, but in the true meaning and spirit. The Holy spirit interprets the law. This then is the next step in the process of freedom.

Jer. 31:33 and Heb 8: 10 "This is the covenant I will make with the house of Israel after that time, declares the Lord. I will put my laws in their minds and write them on their hearts. I will be their God, and they will be my people."

There is no prohibition placed during the period of harvest festival. Yeast was permitted. In fact on that day a pair of bread made with yeast was placed on the shew table in the temple. Two loaves have to be offered at this feast on the shew table instead of the twelve unleavened bread on that day. why did they have to contain leaven? The two loaves represents both the Jews and the Gentiles from which God will take a people unto Himself. These contain leaven, because the believer is not personally free from sin. It is restrained by the Holy Spirit given to them, but not totally eradicated. Though we are not worthy to enter the Holies, the blood of Jesus covers for our sins and has reconciled us with God. (According to the Mishna, the loaves were four handbreadths wide, seven long, and four fingers high) At the time of sacrifices the two lambs (rams) were waved alive, sacrificed as a peace offering for the entire congregation and their breasts and shoulders were laid beside the loaves.

Heb 10: 16-20 "This is the covenant I will make with them after that time, says the Lord. I will put my laws in their hearts, and I will write them on their minds." Then he adds: "Their sins and lawless acts I will remember no more." And where these have been forgiven, there is no longer any sacrifice for sin. Therefore, brothers, since we have confidence to enter the Most Holy Place by the blood of Jesus, by a new and living way opened for us through the curtain, that is, his body.

Pentecost, in the year of the Lord's resurrection, was the day the Church age commenced with the baptism of the Holy Spirit in Jerusalem as recorded in Acts 2:1-4. On this day 3,000 Jewish men were born again as they accepted their Messiah Y’Shua and repented of their sins. Yet on this very same day, back at Mount Sinai 3,000 Jews died at the giving of the Law. While the written word killed, the spirit gave life.

Pentecost as the Betrothal
(http://209.163.251.194/calendar/sivan98/)

In many Sephardic congregations, prior to the Torah reading on the first day of Shavuot, a ketubbah le-Shavuot (marriage certificate for Shavuot) is read, as a symbolic betrothal of God and His people Israel. The terminology of this piyyut (medieval poem), in its various versions, strongly recalls that of the traditional pre-nuptial document (specifying the conditions agreed upon between the two parties; known as tena'im) or the marriage certificate given by the bridegroom to the bride at the betrothal ceremony. In mystical symbolism, the Written Torah is associated with Tiferet and the Oral Torah (the Spirit of God) is linked with Malkhut Jewish mystics interpreted this as the marriage between the written word of God and the Spirit of God the grand culmination of the unification of the sefirot of Tiferet and Malkhut. Shavuot is celebrated, according to the Bible, on one day, as opposed to the other pilgrimage festivals, Sukkot and Pesah (each of which last seven days). Jewish mystics explain that this anomaly is due to the fact that on Shavuot there is complete unity whereas on the other festivals there is merely anticipation of unity.
The hymns which compose this ketubbah le-Shavuot are based on the verses: "I will betroth you unto Me forever; I will betroth you unto Me in righteousness, and in justice, and in lovingkindness, and in compassion. And I will betroth you unto Me in faithfulness; and you shall know the Lord" (Hosea 2:21-22);

Some texts describe the marriage as being solemnized symbolically between the Torah (the bride) and the people of Israel (the bridegroom). God, as the bride's father, gives as dowry the 613 commandments, the Bible, Talmud, and other sacred writings. Moses presents as dowry to his son (the people of Israel) the prayer shawl and phylacteries, the Sabbath and festivals. The contracts are witnessed by God and His servant Moses.

The Book of Ruth, is read on this day as a prescribed reading. . First, the story is centered on the harvest Ruth was a Moabites - a gentile by birth who followed her Mother-in-law into Israel and received the faith of Israel. At the harvest, Naomi's relative Boaz met Ruth, and a fter a short romance Boaz married Ruth. Ruth thus became one of the mothers in the genealogical line of Jesus. The marriage symbolizes the enduring marriage and covenant between the Jewish people that was established at Sinai. It finds its final fulfilment when Jesus betrothed for himself a bride from among the gentiles. This theme is central in all marriages of the East. (See my article on Marriage)

Early Christians recognized the full implication of the Pentecost and considered the event that happened 50 days after the crucifixion of Jesus as the extended fulfilment of the promises. So the Acts of Apostles in describing the events starts thus:

Acts 2:1 And when the day of Pentecost was fully come . . . .

They clearly understood the events as the second full harvest in contrast the primary barley harvest. This time it was not only harvest from the barley but was to be from all fruits of the land, from among both Jews and the gentiles. The first days harvest of life was a 3000 people in contrast to death of 3000 at the mount of Sinai. There were gathered together people from all nations.

Acts 2:1-4 When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.