On one occasion, while he was eating with them, he gave them this command: "Do not leave Jerusalem, but wait for the gift my Father promised, which you have heard me speak about. For John baptized with water, but in a few days you will be baptized with the Holy Spirit."Acts 1:4-5 NIV
But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth."Acts 1:8 NIV
Jesus instructed the disciples to wait in Jerusalem for the Holy Spirit –- the gift, the promise -- that the Father had promised them. They had no idea what they were waiting for exactly or how it would come, but they knew that the Holy Spirit would baptize them in God’s power. The Holy Spirit would come upon them and fill them and change them -- turning them into bold witnesses who would preach the Gospel unto the uttermost parts of the earth with signs and wonders following! They did as Jesus said and on the day of Pentecost the wind of the Holy Spirit blew on them and changed the course of history. The Spirit of God changed them into new creatures that had never existed before (1 Corinthians ) and filled them with the power to change the eternal destinies of billions of people.
When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.Acts 2:1-4 NIV
When the power of God fell on the disciples, they spoke in other tongues as the Spirit gave them utterance. The fire of God was seen on them and they were so loud that people outside the room heard them. People heard them speak in their own languages, telling of the mighty and wonderful works of God! Some people were amazed and some mocked them, calling them drunks, but Peter, who had only weeks before denied the Lord, stood up boldly and proclaimed the Gospel to all the people resulting in three thousand conversions that first day!
Then Peter stood up with the Eleven, raised his voice and addressed the crowd: "Fellow Jews and all of you who live in Jerusalem, let me explain this to you; listen carefully to what I say. These men are not drunk, as you suppose. It's only nine in the morning! No, this is what was spoken by the prophet Joel: "'In the last days, God says, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your young men will see visions, your old men will dream dreams. Even on my servants, both men and women, I will pour out my Spirit in those days, and they will prophesy. I will show wonders in the heaven above and signs on the earth below, blood and fire and billows of smoke. The sun will be turned to darkness and the moon to blood before the coming of the great and glorious day of the Lord. And everyone who calls on the name of the Lord will be saved.'Acts 2:14-21 NIV
"Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ." When the people heard this, they were cut to the heart and said to Peter and the other apostles, "Brothers, what shall we do?" Peter replied, "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. The promise is for you and your children and for all who are far off-- for all whom the Lord our God will call."Acts 2:36-39 NIV
When you get filled with the Spirit of God, you will be filled with boldness to preach the Gospel of the Lord Jesus Christ to all men – those who want to hear and those who don’t. Stephen, who was full of the Holy Spirit, wisdom, faith and power, boldly proclaimed the Gospel in Acts 7 to a hostile audience and was martyred in the process. He was so filled with the power of God that he did not care what they did to him as long as he did what the Lord required of him. When we get filled with the power of God, we will not even be afraid of death, because we are so conscious of God’s presence that we choose to please Him and not man. We do not need to fear man, who can only kill our body -- we need to have respect for God, who is in charge of our eternal destiny (Matthew )! The Holy Spirit gives you the power to please God, not man, and to do great things for God.