The Promise of the Holy Spirit
1 In the first book, O Theophilus, I have dealt with all that Jesus began to do and teach, 2 until the day when he was taken up, after he had given commands through the Holy Spirit to the apostles whom he had chosen. 3 He presented himself alive to them after his suffering by many proofs, appearing to them during forty days and speaking about the kingdom of God.
4 And while staying with them he ordered them not to depart from Jerusalem, but to wait for the promise of the Father, which, he said, "you heard from me; 5 for John baptized with water, but you will 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 times or seasons that the Father has fixed by his own authority. 8 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." 9 And when he had said these things, as they were looking on, he was lifted up, and a cloud took him out of their sight. 10 And while they were gazing into heaven as he went, behold, two men stood by them in white robes, 11 and said, "Men of Galilee, why do you stand looking into heaven? This Jesus, who was taken up from you into heaven, will come in the same way as you saw him go into heaven."
Acts 1:1–11 (ESV)