Pentecost Day is the birthday of the New Testament church. The name is an alternate name for the Jewish celebration of the Feast of Weeks, which occurred fifty (Latin: pente-) days after Passover.

One of the jobs of the Holy Spirit is an empowering of believers for work they could not otherwise do on their own. Most often this is simply the day-to-day life of good works that is impossible for the sinful nature to do on its own.

But at other times the Holy Spirit gives a special empowering for a specific purpose, for example, in the inspiration of the holy writers of Scripture. The most dramatic empowering in the New Testament is of course at Pentecost, where the Holy Spirit filled the disciples for the task of going and announcing the kingdom of God, and on that day gave them the ability to speak in languages they did not know. Yet the speaking in tongues is not the essence of the day. The festival of Pentecost is misconceived when it is only described as a pouring out of special gifts in high measure to the apostles. To celebrate Pentecost properly we must be convinced that today the miracle of the first Pentecost is mystically repeated.

On Pentecost the disciples received the Spirit in such a manner that they now fully understood what the work of Jesus for the forgiveness of sins really meant. In the gospels we notice that the apostles and other disciples were singularly dull regarding the work of Jesus, though they knew his person well enough. But they had no conception what redemption meant. Even up to the day of ascension ten days prior they had false notions regarding the work of Jesus. But all this was changed on Pentecost. In the sermon of Peter on that day we have for the first time clear-cut and definite statements of the forgiveness of sins. Christ was glorified in him and in the other disciples—and that is the gift of Pentecost. That is the precious gift which since then is given to all Christians and is the gift that makes us Christians.

Another job of the Holy Spirit is creation, as in Genesis chapter 1. Pentecost isn’t only an act of empowering, it’s also the re-creation of Israel in fulfillment of Ezekiel 37:1-14. Ezekiel had a vision of the reversal of the decomposition of the human body. The wind brought the Spirit of God which brought those dry bones back to life. At Pentecost, the wind brought the Spirit of God which re-created the people of Israel as the New Testament church. 3,000 people were baptized that day and the church was born.

The tongues of fire are mini-manifestations of God's glory taking up residence in his temple through the Holy Spirit (cp. Exodus 40:34-38, Leviticus 10:2, 1 Kings 8:10). Before this, worshipers of Yahweh needed to make the trip to the temple in Jerusalem several times each year. But since Pentecost the words of Jesus to the Samaritan woman at the well are fulfilled, “A time is coming when you will worship the Father neither on this mountain nor in Jerusalem” (John 4:21). We are all now mobile units of God's presence, and have all taken up the priesthood of our own temples (1 Peter 2:9 combined with 1 Corinthians 3:16 and 1 Corinthians 6:19).

Pentecost is one of the two earliest festivals of the church (the oldest is Easter). The original day fell on an ancient Jewish festival, the Feast of Weeks (Exodus 34:22 and Deuteronomy 16:9-11), which was also called Pentecost by the Jews. It fell exactly seven weeks after the Passover (on which Jesus was crucified one year). It marked the giving of the Law on stone tablets on Mount Sinai, and was therefore the birthday of the Jewish church. It was also observed as a festival of thanksgiving for the completed harvest, when two loaves of bread made from the first wheat were offered to the Lord (Leviticus 23:17).

It is very fitting that this was the day the Holy Spirit should come, who wrote the new law of liberty on tablets of the human heart (Jeremiah 31:33), giving birth to the New Testament church. And at this harvest festival, Pentecost fitly witnessed the first ingathering of souls, the first swaths cut by the Savior’s sickle and made into the bread of God.

In the earliest period of the church, Pentecost was a double celebration of both the ascension and the coming of the Holy Spirit. The Easter day events in Luke’s Gospel are immediately followed by the record of Jesus’ ascension; and in John’s Gospel they are followed directly by the record of the giving of the Holy Spirit. So the themes of Christ’s resurrection, ascension, and the coming of the Holy Spirit formed one celebration in the church.

Today we name the “week of weeks” following Easter day as the Easter season, but up until the 400s the church referred to the entire fifty days as “the seven weeks of Pentecost.” Sometime after A.D. 375 the ascension came to be celebrated separately on its chronological date 40 days after Easter. Soon after that the giving of the Holy Spirit likewise came to be celebrated separately on its chronological date 50 days after Easter.