The Church’s Mission Begins. Luke begins Acts as he began his Gospel, with a foreword to his patron Theophilus, reminding him that the “first book” covered the time until Jesus was taken up by God to heaven. The Gospel ends with a brief reference to this incident (Luke 24:51), which was preceded by important teaching given by Jesus to his disciples. So important was this teaching that we have three accounts of it. Luke records it in the Gospel (Luke 24, especially verses 44–49); he then summarizes it briefly in this introductory part of Acts, and then he covers certain aspects of it once again in the story of the ascension which is the first incident in the main narrative in Acts (1:6–11). The repetition is partly for emphasis, and at the same time it indicates that the period from Easter Sunday to the Ascension is both the conclusion of the earthly ministry of Jesus and the beginning of the work of the church. This period had two important characteristics. It provided evidence that Jesus was alive (1:3),, having risen from the dead, and it was the time when Jesus gave his mission orders to the apostles (1:4f.; cf. 1:7f.).
Jesus had prepared his apostles for their mission by instructing them during his lifetime. He also appeared to them some forty days after his death and resurrection. The forty days seem the same kind of round number as Jesus’ forty days and Moses’ forty years in the desert (Luke 4:1–2 and Exodus). The difference between the ending of Luke’s Gospel and the beginning of Acts does not seem to have bothered Luke. The Gospel treated the ascension as the last event on Easter Day. Acts dates it forty days later.
The disagreements imply that Luke was less concerned with the date of the ascension than with its importance as the event that closed the series of Jesus’ resurrection appearances (except the extraordinary appearance to Paul; compare 1 Cor 15:5–9). Each passage has its own theological message. The Gospel ends with Jesus’ priestly blessing as he ascends (Luke 24:51). Acts compares the ascension to Jesus’ return from heaven (1:11).
Luke also stresses that the risen Jesus gave the apostles convincing signs that he was alive after his death. He appeared several times and continued teaching them what God’s kingdom meant. Since they both saw and heard Jesus risen from the dead, they could be genuine witnesses to his resurrection. Others had only hearsay knowledge about Jesus (e.g., Herod in Luke 9:7–9). Throughout his Gospel and Acts, Luke emphasizes how important it is to both see and hear Jesus. See how Luke contrasts Paul with his companions in Acts 9:3–7.
Luke also underscores how Jesus gave new insights to his disciples after his resurrection. The risen Jesus would give the same kind of instruction to Paul in Acts 9.
The same Holy Spirit who was with Jesus when he chose and instructed the apostles would now be given to them. Both Luke’s Gospel and Acts emphasize that being “baptized by the Holy Spirit” is the way God’s power is given to humans. The Spirit came upon Jesus and thus began Jesus’ mission of preaching and healing (Luke 3:21–22). At Pentecost the same Spirit would be given to the apostles to begin their preaching and healing in Acts. Receiving God’s powerful Spirit far surpasses the effects of John’s baptism, which had merely used water as a sign of repentance (Acts 11:15–17).
Usually in Acts people receive the Spirit when they are baptized as Christians, like the followers of John the Baptist in Acts 19:1–7. But at the very beginning of Christianity, God gave his Spirit to the apostles at Pentecost and to the Gentiles in Acts 10–11 before anyone could give them Christian baptism with water and the Spirit.
These accounts are meant to show how Christianity began by God’s free action, independent of any human cooperation or ritual. The church is not just some human sect, but comes directly from God. The gift of the Spirit which began the church fulfills the Father’s promises in the Old Testament, as Jesus had explained them.