To appreciate Pentecost to the fullest we might savor something of what it meant to people in 5000 B.C.; then, of what it meant to people in 1250 B.C., and finally what it meant to people in 30 A.D.
By 5000 B.C. farm people on the Nile had become well organized in their growing of winter wheat. What they planted in late autumn was ready for harvesting from the day of the first full moon in springtime. On that day they would hand-harvest the first ripe wheat, feasting on the cakes baked without leaven. Then, to get the grain in from the fields before the onset of late spring rains, they set themselves to complete harvesting in fifty days. By working from sunup to sundown for fifty days they completed their work. On the fiftieth day, that they called Pentecost, they would have their wedding parties.
Jesus told a story about a rich man whose harvest was so great that he put off rejoicing, instead he worked hard building bigger barns. In Our Lord’s eyes the man was a fool for not getting the pleasure of God’s rich harvest. Pentecost is a God-given day for rejoicing.
In 1250 B.C. on the night of the first full moon of springtime the Israelites in Egypt baked the first grain of the year in unleavened cakes. Then they set out on a seven-week trek to Mount Sinai. On the fiftieth day, Pentecost, they made their covenant with God. He became their God, and they became his people.
In 30 A.D. Jesus sat down with his Apostles on the feast of the unleavened bread. Then, it was fifty days later, on the ancient farming feat of Pentecost, and the Jewish, feast of Pentecost that the Spirit entered the disciples. Christianity came to life on that ancient feast day when the streets were filled with local farmers and with Parthians Medes and Elamites, and with people from Mesapotamia and Cappadocia. They were all celebrating the wonderful works of God.