All four gospel accounts mention Peter being called by Jesus to be one of His followers. Matthew and Luke provide the most detail:
Now as Jesus was walking by the Sea of Galilee, He saw two brothers, Simon who was called Peter, and Andrew his brother, casting a net into the sea; for they were fishermen. And He said to them, “Follow Me, and I will make you fishers of men.”
Matthew 4:18 & 19, NKJV
Luke 5:1-11 shares the story of Jesus leading Peter and his fellow fishermen to a miraculous catch of fish followed by the instruction that from that point on they would "catch men".
Peter would go on to become a member of Jesus' inner circle, praying, learning, and serving others under the leadership of the One who called him out of fishing into relationship and ministry. Like the other disciples, however, Peter also grew afraid and doubtful as the time of Jesus' crucifixion neared. Luke's account of the situation is clear and concise:
Having arrested Him, they led Him and brought Him into the high priest’s house. But Peter followed at a distance. Now when they had kindled a fire in the midst of the courtyard and sat down together, Peter sat among them. And a certain servant girl, seeing him as he sat by the fire, looked intently at him and said, “This man was also with Him.”But he denied Him, saying, “Woman, I do not know Him.”And after a little while another saw him and said, “You also are of them.”
But Peter said, “Man, I am not!”Then after about an hour had passed, another confidently affirmed, saying, “Surely this fellow also was with Him, for he is a Galilean.”But Peter said, “Man, I do not know what you are saying!”
Immediately, while he was still speaking, the rooster crowed. And the Lord turned and looked at Peter. Then Peter remembered the word of the Lord, how He had said to him, “Before the rooster crows, you will deny Me three times.” So Peter went out and wept bitterly.
Luke 11:54-62, NKJV
Something changed dramatically for Peter in a very short time period. As Jesus went to trial (Passover), Peter adamantly denied being one of His followers. By the time of Pentecost (52 or 53 days later), he was boldly preaching about the same Jesus he had denied less than two months earlier. Consider not just the change in behavior, but the change in attitude as well. What does a man have to see to be transformed from a coward before a young servant girl into a courageous speaker of truth surrounded by crowds of men who passionately disagree with him? Not the words Peter uses to describe what had just happened in the recent memory of the very people to whom he spoke:
“Men of Israel, hear these words: Jesus of Nazareth, a Man attested by God to you by miracles, wonders, and signs which God did through Him in your midst, as you yourselves also know— Him, being delivered by the determined purpose and foreknowledge of God, you have taken by lawless hands, have crucified, and put to death; whom God raised up, having loosed the pains of death, because it was not possible that He should be held by it."
Acts 2:22-24, NKJV
The apostle who is famous for denying he even know Jesus would go on to repeatedly preach and write about the resurrection with absolute confidence for the rest of his life. Here are a few examples:
Blessed be the God and Father of our Lord Jesus Christ, who according to His abundant mercy has begotten us again to a living hope through the resurrection of Jesus Christ from the dead, to an inheritance incorruptible and undefiled and that does not fade away, reserved in heaven for you, who are kept by the power of God through faith for salvation ready to be revealed in the last time.
I Peter 1:3-5, NKJV
In this portion of Peter's first letter, we see no room for denial in defense of life after death for Jesus. It is also apparent that he recognized a connection between the resurrection of Jesus Christ and the future of those who believe in Him. He calls the hope of those who trust Jesus a living hope. Look at the adjectives he ascribes to the inheritance reserved for those with faith: incorruptible and undefiled. Peter writes that are inheritance does not fade away, that is reserved in heaven and we are kept by the power of God. None of the calamities that befall riches, health, and property on earth can touch the inheritance God has reserved for His people. A little later in the same letter, Peter confirms God's work in the lives of His people and again declares the resurrection of Jesus with assurance:
knowing that you were not redeemed with corruptible things, like silver or gold, from your aimless conduct received by tradition from your fathers, but with the precious blood of Christ, as of a lamb without blemish and without spot. He indeed was foreordained before the foundation of the world, but was manifest in these last times for you who through Him believe in God, who raised Him from the dead and gave Him glory, so that your faith and hope are in God.
I Peter 1:18-21, NKJV
Once more, later in the same letter, Peter reiterates the truth of which he is convinced - Jesus Christ rose from the dead:
through the resurrection of Jesus Christ, who has gone into heaven and is at the right hand of God, angels and authorities and powers having been made subject to Him.
I Peter 3:21b-22
Finally, in his second letter, written when his death was imminent, Peter reminds his readers that his account of what happened in his life and in the life of Jesus, he was not making stuff up or citing some mythology to which he had been exposed. Peter was describing events as he experienced them himself! He saw the risen Christ with his own eyes! He walked with Jesus, talked with Him, ate with Him...all after Jesus was brutally, publicly executed on a Roman cross:
For we did not follow cunningly devised fables when we made known to you the power and coming of our Lord Jesus Christ, but were eyewitnesses of His majesty.
II Peter 1:16
Peter is a witness whose transition from scared and silent to courageous and outspoken demands an explanation. Any attempt to rewrite the explanation provided by Peter himself - that he saw death defeated - is misguided in the face of this eyewitness account repeated throughout Peter's life.