“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 ESV).
Jesus, man, sometimes he drops some wild stuff. The Spirit had come upon some of the Old Testament saints. They did some great things for God. David killed the giant. The prophets prophesied. Esther did her thing. But when God's Spirit came upon those Old Testament heroes, it was temporary and rare. He did not stay in them or upon them, nor did he empower all of them.
When Jesus rose, however, the Spirit was set free to regenerate every believer in Christ and his cross. By simple belief -- faith -- people are regenerated by the Spirit of God. Through faith in Christ, we are born again, born of the Spirit. He makes his home in us. He is the down payment, the deposit, the guarantee God is going to redeem our bodies eternally. Forever, we'll be with him, because right now he's in us.
Jesus also said the Holy Spirit would come upon us. Not only would the Spirit live within us, helping us mature and grow and love, but he would come upon us, empowering and enabling us to get it done for God. Jesus told his early disciples that the Spirit would embolden them to testify of Christ throughout the whole world. They'd start in Jerusalem, where they lived at the time, and expand out to the ends of the earth.
The books of Acts records this exact reality. It begins in Jerusalem with Jews and ends in Rome with Gentiles. And it was all accomplished by the power of the Spirit. He came upon, empowered, enabled, and strengthened the believers.
He wills to do the same in you today. If you're a believer in Christ, the Spirit dwells within you. He longs to work through your life. He wills to come upon you and empower you for the work of ministry he's called you to. When confronted with the lion and bear and Goliath, the Spirit of God rushed upon David and aided him in his fight. And he wants to help you on your mission as well. He lives in you to aid you in your Christian walk and discipleship, but he comes upon you to aid you as you fight and labor and testify of Christ.
In the last days we are living in, I am convinced it is the empowering nature of the Holy Spirit we need most. We need his aid and grace and strength to get the job done. The obstacles and arguments in the heart of depraved humanity are too much for our feeble attempts and strategies. No, the only way forward is by the power of the Spirit. He must help us. He must conquer. He must empower us for the work.