Christ's prayers for Peter, that his faith not falter, had sustained Peter as one of Christ's, when the facts on the ground utterly overturned Peter's expectations and false ideas about Messiah's work and purpose, and the future of the Lord's people, and the kingdom of Christ. Peter had looked for a Messiah to rescue and restore Israel, and restore the physical kingdom for Israel immediately. Jesus emphasized the distinction between physical Israel, and Christ's Church. His Church today is not a physical kingdom, but is rather the whole elect called out people of God, saved by the blood of the dying Jesus on the cross. That's when Peter spoke up against Christ, and pushed his own expectations. He denied that Christ must die, and seemed to pay no notice to Christ's promise to rise again the third day. Jesus sharply rebuked Peter for his statements against Christ's death, and warned him that he, Peter, loved the things that the world loves, and not the things that God loves. Man loves power, and force, and the rule of a physical kingdom right now. God loves the sacrifice of Jesus as His Own Lamb, slain to take away the sins of His loved ones, who cannot save themselves from God's wrath. If you reject the Gospel of Christ's death and resurrection, and pursue your own carnal ideas of the kingdom, you will lose your soul and life eternally! In this teaching, Christ was radically overturning and re-orienting Peter's expectations, and showing what things we must value, and what things we must let go of in this life. Peter still resisted Christ's teaching on these matters, which is why Jesus warned him of his impending betrayal, and prayed for his faith to be upheld.