28 But after I am raised up, I will go before you to Galilee.” 29 Peter said to him, “Even though all become deserters, I will not.” 30 Jesus said to him, “Truly I tell you, this day, this very night, before the cock crows twice, you will deny me three times.” 31 But he said vehemently, “Even though I must die with you, I will not deny you.” And all of them said the same.
Famously, after Peter promised this, he did in fact deny that he new Jesus, three times. More interesting, and more important, is how Jesus responds to Peter's denials following the resurrection. This is how John's gospel explains that moment:
15 When they had finished breakfast, Jesus said to Simon Peter, “Simon son of John, do you love me more than these?” He said to him, “Yes, Lord; you know that I love you.” Jesus said to him, “Feed my lambs.” 16 A second time he said to him, “Simon son of John, do you love me?” He said to him, “Yes, Lord; you know that I love you.” Jesus said to him, “Tend my sheep.” 17 He said to him the third time, “Simon son of John, do you love me?” Peter felt hurt because he said to him the third time, “Do you love me?” And he said to him, “Lord, you know everything; you know that I love you.” Jesus said to him, “Feed my sheep.
Peter denies Jesus three times, and three times Jesus asks Peter if he loves him. But Jesus' response is not just about Peter making amends for not backing up his claims. Jesus doesn't simply want him to say that he loves him. He wants him to make the commitment to care for others. "Feed my lambs." "Tend my sheep." "Feed my sheep." It turns out that loving statements don't cure denial. Loving actions do.