Acts 1:1-5 ESV
In the first book, O Theophilus, I have dealt with all that Jesus began to do and teach, until the day when he was taken up, after he had given commands through the Holy Spirit to the apostles whom he had chosen. 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.
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; for John baptized with water, but you will be baptized with the Holy Spirit not many days from now.”
ESV: English Standard Version 2016