18 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.”
19 This He spoke, signifying by what death he would glorify God. And when He had spoken this, He said to him, “Follow Me.”
20 Then Peter, turning around, saw the disciple whom Jesus loved following, who also had leaned on His breast at the supper, and said, “Lord, who is the one who betrays You?”
21 Peter, seeing him, said to Jesus, “But Lord, what about this man?”
22 Jesus said to him, “If I will that he remain till I come, what is that to you? You follow Me.”
23 Then this saying went out among the brethren that this disciple would not die. Yet Jesus did not say to him that he would not die, but, “If I will that he remain till I come, what is that to you?”
24 This is the disciple who testifies of these things, and wrote these things; and we know that his testimony is true.
25 And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written. Amen.
Jesus prophesied (v. 18) that Peter, when he was old, would be crucified (stretch out your hands). Peter referred to this in his second epistle. Knowing that shortly I must put off my tent, just as our Lord Jesus Christ showed me (2 Peter 1:14).
follow Me (v. 19) = tense means “keep on following” — to the end.
Back in John 13:36-37, Peter wanted to follow Christ but couldn’t. Now Jesus tells Peter to follow Him (v. 19). Peter couldn’t follow in his own strength, but God would will him to follow in God’s strength.
Church tradition states that Peter was crucified in Rome under Nero in 65-70 A.D. (upside down at his request because he said he wasn’t worthy to die as Christ had, but this isn’t known for sure).
Jesus’ statement about John’s death (v. 22) wasn’t a prophecy but a statement of His sovereignty.
Verse 25 is the only place in John’s Gospel where the writer refers to himself as “I.”