Today is Pentecost, which occurs on the 50th day – seven weeks – after Easter. In fact, the name comes from the Greek word for “fiftieth” (pentēkostē). The original Day of Pentecost is described in Acts 2, but it was also a Jewish feast, usually called the “Feast of Weeks” (Deuteronomy 16:9-12). There was a Jewish tradition (not in the Old Testament) that the Ten Commandments were given on this day, and that probably forms part of the background to the New Testament event. Here are some significant things about the Day of Pentecost.
The central significance of the Day of Pentecost is the giving of the Holy Spirit. Of course, the Holy Spirit was active in the Old Testament, but his particular indwelling was restricted to some people, such as judges (see Judges 3:10). In this new era, however, the Holy Spirit comes upon all of God's people. This is made clear in Peter's sermon, when he quotes the Book of Joel:
And in the last days it shall be, God declares, that I will pour out my Spirit on all flesh...
(Acts 2:17)
The giving of the Spirit is like a recurrence of the giving of the law on Mount Sinai, since the Holy Spirit is the one who enables us to keep God's law:
And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules.
(Ezekiel 36:27)
The emphasis in the Book of Acts is how the Holy Spirit enables the disciples to proclaim the gospel:
But you will receive power when the Holy Spirit has come upon you, and you will be my witnesses in Jerusalem and in all Judea and Samaria, and to the end of the earth.
(Acts 1:8)
Peter's quotation of Joel also indicates that Pentecost ushers in a new era. It marks the beginning of the last days. It is sometimes called the “birthday of the church”, though we must not forget that the church existed in the Old Testament as well. This new era extends right to the moment of Jesus' return, which is the next item on God's agenda.
Obviously, one of the things that strike us about the Day of Pentecost is the speaking in tongues. However, “tongues” is a loaded word: it would be better to translate it as speaking “foreign languages”. There is a long list of the people groups represented (verses 9 to 11), and the content of the speech is important:
We hear them telling in our own tongues the mighty works of God.
(Acts 2:11)
In this way, Pentecost represents the gospel being proclaimed to all nations, and people from all ethnic groups becoming God's people. In some ways, the Day of Pentecost undoes the consequences of the tower of Babel (Genesis 11): there people were divided by language; now people are united by the gospel, in spite of cultural and language differences.
Speaking in tongues is best seen as a judgment on Jewish people:
For by people of strange lips and with a foreign tongue the Lord will speak to this people...
(Isaiah 28:11)
It therefore represents the movement from Jews to Gentiles that we see in the Book of Acts: because the Jews (generally) rejected Jesus, the offer of salvation goes to the Gentiles.
Finally, the emphasis in Peter's sermon is on the identity of Jesus. Pentecost follows the ascension: the risen and ascended Lord Jesus Christ poured out the Holy Spirit on his disciples:
Being therefore exalted at the right hand of God, and having received from the Father the promise of the Holy Spirit, he has poured out this that you yourselves are seeing and hearing.
(Acts 2:33)
In this way, Pentecost was part of the vindication of Jesus: through the work of the Holy Spirit in the lives of his disciples, it becomes obvious to the world that Jesus is Lord.