1. Matthew 16:16-23 (New International Version, ©2010)
16 Simon Peter answered, “You are the Messiah, the Son of the living God.”
17 Jesus replied, “Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven. 18 And I tell you that you are Peter,[a] and on this rock I will build my church, and the gates of Hades[b] will not overcome it. 19 I will give you the keys of the kingdom of heaven; whatever you bind on earth will be[c] bound in heaven, and whatever you loose on earth will be[d] loosed in heaven.” 20 Then he ordered his disciples not to tell anyone that he was the Messiah.
21 From that time on Jesus began to explain to his disciples that he must go to Jerusalem and suffer many things at the hands of the elders, the chief priests and the teachers of the law, and that he must be killed and on the third day be raised to life. 22 Peter took him aside and began to rebuke him. “Never, Lord!” he said. “This shall never happen to you!”
2. Russian novelist Alexander Solzhenitsyn got it …
…. It was only when I lay there on rotting prison straw that I sensed within myself the first stirrings of good. Gradually it was disclosed to me that the line separating good and evil passes not through states, nor between classes, nor between political parties either, but right through every human heart, and through all human hearts. This line shifts. Inside us, it oscillates with the years. Even within hearts overwhelmed by evil, one small bridgehead of good is retained; and even in the best of all hearts, there remains a small corner of evil.
…. If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?”
3. Jesus knew the thoughts of the heart. Thus, in a very short time span, maybe the same day, he could say to Peter both, “Peter, you are the rock and on this rock I will build my church,” and “Get behind me, Satan, you do not have in mind the concerns of God.”
4. That’s why the mercy and kindness of God always leads to repentance.