The Gospel of John adds the counterweight: after the resurrection, by the same lake, Jesus asks Peter three times "Do you love me?" — one question for each denial — and three times commissions him, "Feed my sheep." Whatever else the early Church believed about Peter, it received him as a man restored, not a man who never fell.
In the Acts of the Apostles, Luke presents Peter as the spokesman of the young Jerusalem community: he preaches at Pentecost, heals, is imprisoned by Herod Agrippa and escapes, and — through a vision at Joppa and the baptism of the Roman officer Cornelius — becomes the apostle who first opens the movement to non-Jews. This is history-shaped narrative written by Luke, not Peter's own memoir, but it is our earliest sustained portrait of him. Paul independently corroborates two things: Peter (whom he calls Cephas) was a recognized pillar of the Jerusalem church, and the two men clashed sharply at Antioch over table fellowship with Gentiles (Galatians 2:11–14) — a genuine, awkward dispute that no later admirer would have invented.
What happened next passes from record into tradition. The New Testament never places Peter in Rome. But from the late first century onward — Clement of Rome (c. 96), then Ignatius, Irenaeus, Tertullian, and Origen — a consistent memory holds that Peter ministered and died in Rome as a martyr under Nero, around AD 64–68. The detail that he was crucified head-downward, judging himself unworthy to die as his Lord did, first appears in the apocryphal Acts of Peter (second century) and should be read as pious legend, along with the famous "Quo vadis?" encounter from the same text. Bones excavated beneath St Peter's Basilica in the twentieth century were declared by Paul VI in 1968 to be "most likely" Peter's — a claim that remains, honestly, unproven. Two New Testament letters bear his name, but most scholars judge both to be written later in his name (see works).