What does John 21:19 mean?

Jesus poetically asked Peter to affirm his love three times (John 21:15–17), after Peter denied knowing Jesus three times (John 13:36–38; Luke 22:61–62). When Jesus first called Peter, it was just after miraculously providing an enormous catch of fish (Luke 5:5–11). Here, after a similar miracle (John 21:4–8), Jesus will again restore Peter's calling as an apostle.

In the prior verse, Jesus used a descriptive parallel. In youth, Peter could dress himself and walk where he chose, but in death he would be dressed and led by others, with outstretched hands. As this verse notes, Jesus has predicted how Peter would die: by crucifixion. Awful as that may be, it is also a prediction that Peter's restored faith would never fail again. He would make mistakes (Galatians 2:11–14), but never deny Christ, even in the face of his own death.

Church tradition affirms that Peter was crucified. Further details suggest he asked to be hung upside down, symbolic of his inferiority to Jesus. That prediction will make Peter curious about his fellow disciples, leading to the question he asks in the next verses (John 21:20–21).