How does Peter in Acts differ from Peter before the crucifixion?
Before the crucifixion, Peter was fearful and denied Christ three times to save his own life. After the Resurrection, and especially in Acts, he is a totally different person, ready to go to the ends of persecution because he witnessed Christ's real, bodily resurrection.
Les explains that when Christ was first arrested, the disciples were scattered like quail and scared to death. Peter denied Him three times because he was fearful for his own life. That was typical. But after the Resurrection, that kind of attitude is gone. Peter and the rest are ready to go to the very ends of persecution, knowing that no matter what happens to them physically, the power of the Resurrection is still in our future. Les emphasizes that Peter, especially as we go into the Book of Acts, is a totally different person than he was leading up to the crucifixion because he had witnessed the power of Christ's resurrection. It was not a figment of someone's imagination; it was real. Les then points to Luke 24 to show that Christ arose bodily.