How can I stand firm until the end? What if we’re wrong about all this? How can I have confidence that the Christian gospel is true? Consider the concluding words from Peter in 1 Peter 5:12 — this is the true grace of God.
Peter believed this was true. We know this from a brief look at Scripture and the pages of church history. In Scripture, Jesus predicted how Peter would die. IN John 21:18-19, Jesus said this to Peter: “Truly, truly, I say to you, when you were young, you used to dress yourself and walk wherever you wanted, but when you are old, you will stretch out your hands, and another will dress you and carry you where you do not want to go.” (This he said to show by what kind of death he was to glorify God.) And after saying this he said to him, “Follow me.”
Based on multiple sources from church history, we believe that Peter died in Rome, within a few years after the completion of 1 Peter. Probably not long after writing the second letter that bears his name. By that point Nero’s persecution had begun, and naturally a man like Peter would be high on Nero’s list to capture and execute. Historians record that Peter’s hands were indeed stretched out in his death, since Peter died by crucifixion. The story goes that Peter was crucified upside-down, not worthy to die in the same manner as his Lord.
Bible teacher Daniel Doriani helps us understand why the crucifixion of Peter should help the Christian have confidence in the truthfulness of the Gospel. He writes:
“People do die for a lie, especially if someone has duped them into believing it. People may even die for something they know to be a lie (think of the lies of communism), if it promised them great wealth or power. But people do not die for a lie that they know they invented, especially when that lie brings them no benefit, and causes them nothing (in this world) but danger, suffering, and loss. The apostles [including Peter himself] died for the testimony to the words and works of Jesus, which is the strongest evidence that they knew it was true.”
Stand firm until the end because it’s all true.
 Daniel Doriani, Reformed Expository Commentary: Matthew, chapter 28 https://ref.ly/logosres/rec61mt?ref=Bible.Mt8.1-4&off=19543