It's a thing of beauty: a glistening silver 1955 Porsche 356 two-door convertible. You can almost feel yourself drooling as you look inside and see the plush black interior, and the speedometer that tops out at 140 mph. The spotlights in the auto museum highlight the finish on the glossy paint and the lovingly applied layers of high-grade wax.
But if you wanted to hear the roar of the four-cylinder horizontally opposed engine, you would be in for a big disappointment: There is no gas in the tank. Nobody intends to drive this car, and it would be foolish to put gas in the tank of a car that nobody intends to drive.
Just before Jesus left earth, he told his gathered disciples that they would receive power when the Holy Spirit came on them — power to be His witnesses to the world, spreading the good news of Jesus' victory to everybody, and to effectively lead people to the Lord for salvation. (See Acts 1:8.)
Ten days later, these same disciples were filled with the Holy Spirit during the feast of Pentecost. And, as a result of that filling, the testimony of Peter, backed by the other apostles, brought 3,000 people into the kingdom of heaven.
A short time later, after the miraculous healing of a man who had been lame for decades, another couple thousand people became believers in Jesus. The power really was doing its job.
Over the next few years, more and more people came to believe in Jesus through the Spirit-empowered testimony of his followers. These filled-to-the-brim believers rocked all of Jerusalem with the message of salvation, and then, when persecution scattered them to the surrounding countryside, they rocked the rest of the country as well! True to Jesus' word, they powerfully preached the gospel to the ends of the earth.
These days, a lot of people have a woefully inadequate view of what the life of a Spirit-filled Christian is supposed to look like. Jesus promised his disciples power when the Holy Spirit filled them, but it was power for a specific purpose: to be a witness.
When the disciples had been warned by the Jewish leaders not to preach in the name of Jesus anymore under threat of punishment, they prayed an amazing prayer with a plea for great boldness in witnessing. And the very next verse tells us that "After they prayed, the place where they were meeting was shaken. And they were all filled with the Holy Spirit and spoke the word of God boldly." (Acts 4:31 New International Version) The Lord answered with a fresh filling of the Holy Spirit to empower their witness!
A lot of people want to be filled with the Holy Spirit for the benefits that it brings them, comfort, a sense of God's presence and cleansing of inner sin. And the Holy Spirit can do all of those things.
But if that is as far as we take it, we end up like polished statues of saints sitting on a shelf somewhere: nice to look at, but pretty worthless when it comes to the actual work of the kingdom. Like the Porsche 356 in the auto museum, we look good on the outside, but we have no power inside to actually DO anything. And the fact is, just like it doesn't make any sense and would be a total waste of a good resource to put gas into the engine of a car that you don't intend to drive, it is a total waste of time for God to fill anyone with the Holy Spirit who never intends to immediately use that world-shaping, life-creating, evil-banishing power to boldly witness to the unsaved about what the Lord has done in their lives.