Acts 13 contains the first of several “sermons” given by Paul. Luke is clearly summarizing since the sermon is a mere 25 verses long, taking no more than a couple of minutes to read. Since the sermon follows the blinding of Bar-Jesus, it is likely that the sermon serves as an explanation of the events on Cyprus, but it is also a representative “synagogue” sermon for Paul.
Schnabel points out that there are three movements in the sermon (Paul the Missionary, 158-9). Paul first reviews Israel’s history from the Patriarchs through John the Baptist (v. 16-25). In the second movement, Paul declares the importance of Jesus in the light of this history (v. 26-37). It is in this section that Paul carefully weaves several texts form the Hebrew Bible together to make the point that Jesus fulfils the promise made to Abraham. The final part of the sermon is the call to repentance (verse 29-41). Like Peter and Stephen, Paul calls his listeners to respond to the message that Jesus is the Christ, although the repentance here in Paul’s sermon is not related to the killing of Jesus, nor does he declare that the “times of refreshing will come.” Now repentance is connected with justification and forgiveness of sins (verses 38-39).
This is a significant development. In Acts 2 and 3, Peter’s sermon was directed at people who had themselves witnessed the events of the crucifixion and resurrection, and even participated in those events (cf. 2:23). No one in the synagogue at Antioch would have been at Jerusalem so they could not be accused of participating in the crucifixion. Paul’s sermon adds a new element – forgiveness of sins. But there is a radical element here: Paul says that through Jesus one can have forgiveness of sins in a way that the Mosaic Law could not provide (37-38).
While the first parts of this sermon were quite similar to that of Peter and Stephen, Paul now calls for a much different response than Peter did. Peter declared that those who repent will be a part of the coming kingdom. In Acts 2 and 3 the repentance is of a sin of ignorance, the sin of killing the Messiah. Since the people acted in ignorance, they may repent and find forgiveness.
Now Paul says that the “one who believes is justified,” but in a way that the Law could never justify. There is a great deal of “Pauline theology” in this verse, since the Mosaic Law allowed for “sins of ignorance” to be forgiven through a sacrifice. If one sinned intentionally (“with a high hand”) then a sacrifice could not be made. Deliberate, premeditated breach of the Law could not find “justification” through a sacrifice. Paul is not talking about the sin of killing the Messiah, but rather of deliberate sins done with forethought and intention, and he is saying that one who believes is the one that receives justification.
Is this a development away from the Law? I think so, Paul is declaring that God granting forgiveness in a new way, one that might very well have been unanticipated in the Hebrew Bible.