When the day of Pentecost had come, they were all together in one place. And suddenly from heaven there came a sound like the rush of a violent wind, and it filled the entire house where they were sitting. Divided tongues, as of fire, appeared among them, and a tongue rested on each of them. All of them were filled with the Holy Spirit and began to speak in other languages, as the Spirit gave them ability. Now there were devout Jews from every nation under heaven in Jerusalem. (Acts 2:1-5)
Jerusalem was full at this time because Jews had travelled in from all around to celebrate Pentecost.
For a first-century Jew, Pentecost was the fiftieth day after Passover. It was an agricultural festival. It was the day when farmers brought the first sheaf of wheat from the crop and offered it to God, partly as a sign of gratitude and partly as a prayer that all the rest of the crop, too, would be safely gathered in.
But, for the Jew, neither Passover or Pentecost were simply agricultural festivals. These festivals echoed the great story of their forefathers. The Passover remembers the exodus from Egypt when God fulfilled his promises to Abraham by rescuing his people. They sacrificed a lamb just like they did the night they left Egypt and crossed the red sea into the Sinai desert.
50 days after days after Passover, after crossing the red sea, they came to Mount Sinai, where Moses received the law, on the stone tablets. Pentecost then isn’t just about the first fruits, the sheaf of wheat which says the harvest has begun. it’s about God giving to his people the way of life by which they must now life, giving them the 10 commandments.
So as we hear about what happened to the first disciples as the holy spirit came upon them at Pentecost, Luke, the writer of the book of acts takes it for granted that we would remember that Pentecost is about the first fruits of the harvest and the giving of the law on stone tablets.
Now we see the first disciples being filled with spirit and then going on to bear powerful witness to Jesus and his resurrection to win converts from the very first day, this like the sheaf of wheat which is offered to God is a sign of the great harvest to come.
And whereas Moses and Israel were given the law written on Stone tablets, here the disciples receive the holy spirit into their hearts.
Pentecost then is the first fruits of the Kingdom of God, the outpouring of the Holy Spirit, the moment when we move from stone tablets to God dwelling within us.
Jeremiah tells us this was God’s plan when he said:
The days are surely coming, says the Lord, when I will make a new covenant with my people. It will not be like the covenant that I made with their ancestors when I took them by the hand to bring them out of the land of Egypt—a covenant that they broke, says the Lord.
But this is the covenant that I will make with the house of Israel after those days, says the Lord: I will put my law within them, and I will write it on their hearts; and I will be their God, and they shall be my people. No longer shall they teach one another, or say to each other, “Know the Lord,” for they shall all know me, from the least of them to the greatest, says the Lord; for I will forgive their iniquity, and remember their sin no more. (Jeremiah 31:32-35)
We are God’s forgiven people through the power of the cross and we can know God because His holy spirit lives within us.