Too many evangelicals see the good news that we are saved from sin and from God's wrath and stop there. We forget that we are saved for a relationship with God (to know Him and love Him) and for His mission (His redeeming work to seek and save the lost). And it's the Holy Spirit that enables that relationship and empowers us for mission.
Old Testament Promises
We don't have to search the Scriptures very far to see that just as Jesus was foreshadowed and prophesied in the Old Testament, so was the Holy Spirit's coming.
Take for example the prophecy of Jeremiah, in chapter 31. We love the phrase in verse 34, where God says:
For I will forgive their wrongdoing and never again remember their sin.
Glory to God for His purposeful forgetfulness!
Isn't that the beauty of the gospel? We purposefully remember the truth that God purposefully forgets? That's what the Lord's Supper is all about. We commit to memory God's commitment to forgetfulness. To never bring up our sins again.
But note the promise that comes just before that verse:
They will all know me, from the least to the greatest of them.
And just before that:
I will place My law within them and write it on their hearts. I will be their God, and they will be my people.
See the context? It's not just forgiveness of sins. It's new hearts resulting in a restored relationship.
Or consider Ezekiel 36. Here's the promise we receive from the Lord in verse 25:
I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your impurities and all your idols.
What a glorious promise! To be cleansed of sin and delivered from idolatry. But that's only half of what God promises through the prophet Ezekiel. Verse 26:
I will give you a new heart and put a new spirit within you; I will remove your heart of stone and give you a heart of flesh. I will place My Spirit within you and cause you to follow My statutes and carefully observe My ordinances.
In other words, not only will God wipe away our sins, He will give us His Spirit, restore our relationship with Him, and enable us to obey. The promise of the gospel is not only that we are forgiven, but that we are made new.
New Testament Fulfillment
With the Old Testament promises in the background, it's no wonder that in his sermon at Pentecost, Peter moved from proclamation of Jesus to proclamation of the promise of the Spirit?
"Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit."
Forgiveness of sins is only half of the promise. When we repent and believe, God doesn't just clean up a bad heart; through the Spirit, He gives us a new heart. It's not that God does open-heart surgery. He gives us a heart transplant!
God doesn't just wipe the slate clean of our disobedience; He indwells us so that we will long for obedience. He doesn't just offer His forgiveness; He offers Himself - in relationship to us.
Pentecost as a Turning Point
Acts 2 records a turning point in the history of the world.
My wife (who is Romanian) has gotten me scratching my head about why we don't celebrate Pentecost in non-liturgical churches in the U.S. The Baptists and Pentecostals in Romania would take an entire weekend every year, 50 days after Easter, to celebrate the coming of the Spirit. Her quip was: It seems weird that churches in the U.S. will celebrate the birth of their country in church but not the birth of the church.
I believe this is a significant oversight. Christmas, Good Friday, Easter Sunday are not the end of God's mighty works in salvation history. Pentecost is absolutely essential for you to live the Christian life. Just as in the days of Peter, the Spirit of God pierces us to the heart when we hear the gospel message. Thank God for the scalpel of the Spirit! He is the One who fills us, who uses us, who works through us, who convicts us.
We believe in a God who keeps His promises. He promised the Spirit and He kept His promise. That's good news!
(For more along these lines, I recommend the first chapter of Darrell Bock's book, Recovering the Real Lost Gospel: Reclaiming the Gospel as Good News as well as the chapter on Pentecost in Scot McKnight's A Community Called Atonement and Malcolm Yarnell's contribution on the Holy Spirit in A Theology for the Church.)