As we saw, Peter knew that he was soon to die. And he knew (and for a long time, too), how he was going to die. That’s because Jesus Himself had told him. “‘Most assuredly, I say to you, when you were younger, you girded yourself and walked where you wished; but when you are old, you will stretch out your hands, and another will gird you and carry you where you do not wish’” (John 21:18, NKJV).
What was his end?
“Peter, as a Jew and a foreigner, was condemned to be scourged and crucified. In prospect of this fearful death, the apostle remembered his great sin in denying Jesus in the hour of His trial. Once so unready to acknowledge the cross, he now counted it a joy to yield up his life for the gospel, feeling only that, for him who had denied his Lord, to die in the same manner as his Master died was too great an honor. Peter had sincerely repented of that sin and had been forgiven by Christ, as is shown by the high commission given him to feed the sheep and lambs of the flock. But he could never forgive himself. Not even the thought of the agonies of the last terrible scene could lessen the bitterness of his sorrow and repentance. As a last favor he entreated his executioners that he might be nailed to the cross with his head downward. The request was granted, and in this manner died the great apostle Peter.” – Ellen G. White, The Acts of the Apostles, pp. 537, 538. And yet, even with this prospect before him, Peter’s concern was for the spiritual well-being of the flock.
Source: Daily Sabbath School Lessons