Acts 1:1-9 NRSV
In the first book, Theophilus, I wrote about all that Jesus did and taught from the beginning until the day when he was taken up to heaven, after giving instructions through the Holy Spirit to the apostles whom he had chosen. After his suffering he presented himself alive to them by many convincing proofs, appearing to them during forty days and speaking about the kingdom of God. While staying with them, he ordered them not to leave Jerusalem, but to wait there for the promise of the Father. “This,” he said, “is what you have heard from me; for John baptized with water, but you will be baptized with the Holy Spirit not many days from now.”
So when they had come together, they asked him, “Lord, is this the time when you will restore the kingdom to Israel?” He replied, “It is not for you to know the times or periods that the Father has set by his own authority. But you will receive power when the Holy Spirit has come upon you; and you will be my witnesses in Jerusalem, in all Judea and Samaria, and to the ends of the earth.” When he had said this, as they were watching, he was lifted up, and a cloud took him out of their sight.
NRSV: New Revised Standard Version