Acts 1:1-3

Acts 1:1-3 NASB

The first account I composed, Theophilus, about all that Jesus began to do and teach, until the day when He was taken up to heaven, after He had by the Holy Spirit given orders to the apostles whom He had chosen. To these He also presented Himself alive after His suffering, by many convincing proofs, appearing to them over a period of forty days and speaking of the things concerning the kingdom of God.
NASB: New American Standard Bible