Acts 1:1–3 (Listen)

1:1 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.

(ESV)