From Acts of the Apostles Chapter 1:
When they had gathered together they asked him, "Lord, are you at this time going to restore the kingdom to Israel?"
He answered them, "It is not for you to know the times or seasons that the Father has established by his own authority.
"But you will receive power when the Holy Spirit comes upon you, and you will be my witnesses in Jerusalem, throughout Judea and Samaria, and to the ends of the earth."
When he had said this, as they were looking on, he was lifted up, and a cloud took him from their sight. While they were looking intently at the sky as he was going, suddenly two men dressed in white garments stood beside them.
They said, "Men of Galilee, why are you standing there looking at the sky? This Jesus who has been taken up from you into heaven will return in the same way as you have seen him going into heaven."