Israel's worship of the Lord and part of their covenant responsibility was to celebrate a series of annual feasts.
The feasts established by the Lord can be divided into the spring feasts (Passover, Unleavened Bread, Firstfruits, Feast of Weeks) and fall feasts (Trumpets, Day of Atonement, Feast of Tabernacles). The fall feasts would begin in the seventh month (Sept/Oct) when the dry, hot summer came to an end. Harvest would include the picking of the grapes and the olives. By the end of October the rains would begin and continue until March.
Leviticus 23:4-8 - Passover and Unleavened Bread – Passover was the greatest feast of the year and commemorated the greatest event in Israel’s history – The Lord’s deliverance from Egypt. The use of unleavened bread commemorates the historical fact that Israel left Egypt in haste (not in waves of escaped slaves, or due to changes in Egypt’s economic conditions) because of Pharaoh’s sudden decision to let the Hebrew slaves go after the plague of the death of the firstborn. It was a deliverance by the Lord and it was in haste! Go! Get out of the land!
Leviticus 23:9-14 – Feast of Firstfruits – This feast was closely associated with the Passover. The firstfruits of the spring would have been barely. There would be a presentation of the sheaf on the day after the Sabbath which symbolized the dedication of the whole year’s crop. Nothing of this year’s crop could be eaten until the firstfruits were offered.
Leviticus 23:15-22 - Festival of Weeks (Pentecost) – Is also called the Feast of Harvest in Exodus 23:16. This feast would occur seven weeks and one day after Sabbath after the full moon of the Passover, so somewhere from the end of May to mid-June as the wheat harvest was ending. All the men would have to appear at the Tabernacle.
Leviticus 23:23-25 - Festival of Trumpets – This was a one day celebration that receives no emphasis here or throughout the rest of the Old Testament. The focus of this feast seems to be the accurate establishment of the beginning of the seventh month. It was a sort of synchronizing of their watches, or, in this case, their calendars.
Leviticus 23:26-32 - Day of Atonement – This was the most solemn and holy day. While the high priest was busy with the sacrifice of the bull for his sins and the two goats (one was sacrificed for the people and the other was released into the wilderness with the sins of the people) the people were to be fasting, repenting and not working. This feast cleansed the Tabernacle of the rebellion and sin of the people and the priests, while covering their sins for another year.
Leviticus 23:33-44 - Festival of Tabernacles – For one week the people were to leave their homes and live in shelters made of branches. This was to remind them of having once lived in tents wandering in the wilderness for forty years. They could reflect on what it takes to be a great, robust culture and how dependence on God’s leadership and provision is crucial. They could be thankful that diligence to hard work and obedience to God’s law provided them with their good land, their abundant provisions and their nice homes. Or, as Deuteronomy 8:11-14 tells them:
“Be careful that you do not forget the Lord your God, failing to observe his commands, his laws and his decrees that I am giving you this day. Otherwise, when you eat and are satisfied, when you build fine houses and settle down, and when your herds and flocks grow large and your silver and gold increase and all you have is multiplied, then your heart will become proud and you will forget the Lord your God, who brought you out of Egypt, out of the land of slavery.”
Two other feasts that are not original to the Law of Moses, but are celebrated by Jews today are Purim, which was established as a result of the deliverance of the Jews by Esther in Persia, and Hanukkah, which celebrates the deliverance of Israel from the Syrians and the rededication of the temple in 165 BC by Judas Maccabaeus.
It should be noted that Jesus’ redemptive work occurred on Passover, Unleavened Bread, and Pentecost, so that today Christians celebrate Jesus death on Passover, his Resurrection on the Feast of Unleavened Bread, and the coming of the Holy Spirit into the church on Pentecost. The dates do not always match up any longer since there has been 2,000 years of adjustments to the different calendars.