Let us look more closely at the scripture to see what the Holy Spirit does when He comes to abide within. "And being assembled together with them, He commanded them not to depart from Jerusalem, but to wait for the Promise of the Father, 'which,' He said, 'you have heard from Me; for John truly baptized with water, but you shall be baptized with the Holy Spirit not many days from now.' Therefore, when they had come together, they asked Him, saying, 'Lord, will You at this time restore the kingdom to ?' And He said to them, 'It is not for you to know times or seasons which the Father has put in His own authority. But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth'" (Acts 1:4-8).
Here we are told that when the Holy Spirit came, the disciples would receive power. What was this power for? Jesus said, "You shall be witnesses to Me." Naturally these disciples could give a firsthand, eyewitness account of all they had seen, including the death and resurrection of Jesus. But to give that "witness to Christ," they needed something beyond themselves. They needed the power of God. We have already mentioned how Peter stood before all Jerusalem and gave witness to what had taken place. "And with great power the apostles gave witness to the resurrection of the Lord Jesus. And great grace was upon them all" (Acts 4:33). "And through the hands of the apostles many signs and wonders were done among the people. And they were all with one accord in Solomon's Porch" (Acts 5:12).
The power that was manifest through these men was more than just ability to speak words. There was a grace or ability that was beyond natural explanation. God was now dwelling within them, revealing Himself through them. It was the fulfillment of these words from Jesus: "Most assuredly, I say to you, he who believes in Me, the works that I do he will do also; and greater works than these he will do, because I go to My Father. And whatever you ask in My name, that I will do, that the Father may be glorified in the Son. If you ask anything in My name, I will do it" (John 14:12-14). As we read through the book of Acts we see the "acts of the Holy Spirit" through men: not just men who were convinced that Jesus was God, but a continuation of the manifestation of the life of Jesus through men.
The power that these men received was not separate from God but rather the power that comes with the presence of God. God had come to abide within, and when God comes He brings all that He is. We cannot know the attributes of God separate from God, and when the Holy Spirit (God) comes to abide, He does not come in part. "For He whom God has sent speaks the words of God, for God does not give the Spirit by measure" (John 3:34). When a person receives the Holy Spirit, he does not receive some "thing." He receives God, and in receiving God within he receives all that God is. That is why Paul could say: "To them God willed to make known what are the riches of the glory of this mystery among the Gentiles: which is Christ in you, the hope of glory. Him we preach, warning every man and teaching every man in all wisdom, that we may present every man perfect in Christ Jesus. To this end I also labor, striving according to His working which works in me mightily" (Col. 1:27-29).
Many times it is held before us that we need power to "witness for Jesus" and "do work for God." While there may be some truth in these statements, I believe there is a greater truth that we need to grasp: that God has not called us to just "tell people about Jesus," but to live the very life of God as a son of God. We are called to be a living witness unto the character of God, and to do that we need a power that is not of ourselves. Strictly speaking, we do not "work for God," but rather God works in us to do His will. That working becomes real as we abide in Christ and He in us. Out of this union, works will come forth that are works of God (or works of the Holy Spirit). These works are expressed in vessels of clay, but they are expressions of the divine presence of God--visible expressions of the power of God. In simple words, we need power to be what God has called us to be: sons of God.