Pentecost is this Sunday. The curious among us might ask why, when the liturgical calendar is based on 40 day intervals (end of Apokreas-Easter) (Easter-Ascension) (Christmas-Presentation in the temple etc) does the calendar suddenly shift to a 50 day interval?
The Hebrews had a system of delivering a portion of the first fruits of seven crops (barley, wheat, figs, pomegranates, grapes as wine, olive oil and dates) to the temple as a sacrifice. The first “fruit” was barley and was offered the day after Passover. The “Omer” ritual was the daily counting of the 50 days between the barley offering and the next offering, the new wheat. The counting ritual is called “counting the Omer”. The wheat offering was called the feast of Shavuot.
One of the functions of counting the 50 days was to spiritually prepare the people for the Shavuot feast which also signified the reception from God by Moses of the laws and knowledge contained in the Torah (Ten Commandments +) on Mount Sinai. In the story, God actually appeared on the mountain in the form of a storm cloud and spoke to the Israelites in a language all could understand. The wheat harvest and the reception of the Torah coincide. It was/is an important feast.
In early Judeo-Christianity the tradition of observing Shavuot continued and linked the feast day with the end of the 50 day period of mourning Christ. The Christian version says that the family, Apostles and other followers of Christ gathered to note the end of mourning and to celebrate Shavuot. God appeared to the gathering in the form of a great wind and bestowed to them the gift of the ability to communicate wisdom in all languages.
The adaptation to Christianity of the appearance of a wisdom-bestowing God seems obvious.
Jewish traditions must derive from even earlier rites of Semitic polytheistic observances. It is clear that the ancient offering of first fruits to one or many deities was an important and necessary ritual for cultures dependent on agriculture for survival. The Hebrews were not alone. Other groups, including the Ancient Greeks, did the same
Pentecost in Orthodoxy is a feast second only to the Easter celebration. The clergy wear green vestments and the churches are decorated with greenery in recognition to the Old Testament Shavuot.