The “first book” (1:1) is the Gospel of Luke, dedicated (like Acts) to Theophilus (Luke 1:3). The scope of that earlier work is indicated as “all that Jesus began to do and teach, until the day when he was taken up” (1:1, 2). The implication is that this second book will deal with what Jesus continued to do and teach after the day when he was taken up by his Spirit in his followers. The forty days were days of necessary preparation for the disciples. Jesus had often spoken to
Acts 1:1–11