Where in the Bible does it say that Peter was crucified upside down?

AnswerThe Bible provides no information about how or why Peter died. The traditions that Peter was executed and that this was by an unusual form of crucifixion arose later in the Christian Church. The venerable Polycarp of Smyrna had tried to win an argument with the mid-second century pope Anicetus (156-166) on a matter of theology, by saying that he spoke with the authority of the apostle John. In response, Anicetus said that Peter was beheaded by Nero in Rome and that he spoke with the authority of Peter. In this first mention of Peter's death, he was beheaded, not crucified. Then in the third century, the Church Father Origen changed the story somewhat, saying that Peter, condemned to crucifixion, felt himself unworthy to be crucified the same way as his Lord, and so chose crucifixion upside down.

Catholic Answer:

Nearly 2000 years of Catholic tradition have Peter martyred during the reign of Nero sometime between the years 64-67. He was crucified upside down by his own request. As to the statement purportedly made by Pope Anicetus, it never happened. Virtually nothing is known about the reign of this pontiff. All that is recorded is that he had a visit from Saint Polycarp to discuss the date when Easter should be observed. Both agreed to disagree and parted amicably.