Peter was crucified upside down because, according to Christian tradition, he requested it that way as a sign of humility. He did not consider himself worthy to die in the same manner as Jesus Christ, who was crucified upright. This tradition is first recorded in the late 2nd-century apocryphal text called the "Acts of Peter," where Peter himself requests to be crucified with his head downward. The upside-down crucifixion of Peter is symbolic and serves a theological purpose, representing the idea that the world is turned upside down by sin and that through Christ, this is restored. While this story is widely accepted in Christian tradition, it is not mentioned in the Bible and historical evidence is inconclusive. The earliest church father to mention Peter's upside-down crucifixion was Origen in the mid-3rd century, and Jerome later wrote that Peter felt unworthy to die in the same way as Jesus. The tradition likely originated partly as a symbol of Peter's humility and partly as a narrative illustrating theological ideas about sin, repentance, and restoration through the cross.