A witness of the resurrection

（1） This sermon is not actually a record of Peter and Paul's story. Especially in Paul's story, there is no idea that can be said to be the core of Paul's theology. Paul who wrote to Rome and Corinth is different from Paul who is talking in the Acts. Diberius and others. say that these sermons are the examples of preachings commonly heard in churches around 90 years  where the Acts of the Apostles were written. 
(2) These sermons are all based on the liturgical text that the church originally had. In other words, the personal character of the person who actually wrote the gospel, such as Peter and Paul and the author of Luke, cannot be seen at all. It is the same person who wrote the Luke Gospel and the Acts. In the Acts, he borrowed the names of the Apostles Peter and Paul to show a sample of a very traditional preaching at that time.

Looking closely at it, these stories are mostly in the form of the Apostolic Creed. And so, all these beliefs of the early church's faith are in the resurrection of Jesus Christ. The mission of the disciples was to “become a witness of the resurrection of the Lord” (Acts 1–22). In other words, disciples are those who become witnesses of the Lord's resurrection. Thus, the author of Luke himself wrote the Gospels and the Acts as one of the things to become a true witness of Christ.