Acts 1:8 is a key verse. To begin with, it explains that the power of the church comes from the Holy Spirit and not from man (see Zech. 4:6). God’s people experienced repeated fillings of the Spirit as they faced new opportunities and obstacles (Acts 2:4; 4:8, 31; 9:17; 13:9). Ordinary people were able to do extraordinary things because the Spirit of God was at work in their lives. The ministry of the Holy Spirit is not a luxury; it is an absolute necessity.

“Witness” is a key word in the Book of Acts and is used twenty-nine times as either a verb or a noun. A witness is somebody who tells what he has seen and heard (Acts 4:19–20). When you are on the witness stand in court, the judge is not interested in your ideas or opinions; he only wants to hear what you know. Our English word martyr comes from the Greek word translated “witness,” and many of God’s people have sealed their witness by laying down their lives.
-Wiersbe

Acts 1:1–11 (MEV)

1 The former treatise have I made, O Theophilus, concerning all that Jesus began both to do and teach,

2 until the day when He was taken up, after He had given commandments through the Holy Spirit to the apostles whom He had chosen,

3 to whom He presented Himself alive after His passion by many infallible proofs, appearing to them for forty days, and speaking concerning the kingdom of God.

4 Being assembled with them, He commanded them, “Do not depart from Jerusalem, but wait for the promise of the Father, of which you have heard from Me.

5 For John baptized with water, but you shall be baptized with the Holy Spirit not many days from now.”

6 So when they had come together, they asked Him, “Lord, will You at this time restore the kingdom to Israel?”

7 He said to them, “It is not for you to know the times or the dates, which the Father has fixed by His own authority.

8 But you shall receive power when the Holy Spirit comes upon you. And you shall be My witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.”

9 When He had spoken these things, while they looked, He was taken up. And a cloud received Him from their sight.

10 While they looked intently toward heaven as He ascended, suddenly two men stood by them in white garments.

11 They said, “Men of Galilee, why stand looking toward heaven? This same Jesus, who was taken up from you to heaven, will come in like manner as you saw Him go into heaven.”