Read Mark 8:27-38
27 Then Jesus and his disciples went away to the villages near Caesarea Philippi. On the way he asked them, “Tell me, who do people say I am?”
28 “Some say that you are John the Baptist,” they answered; “others say that you are Elijah, while others say that you are one of the prophets.”
29 “What about you?” he asked them. “Who do you say I am?”
Peter answered, “You are the Messiah.”
30 Then Jesus ordered them, “Do not tell anyone about me.”
(Matt 16:21–28; Luke 9:22–27)
31 Then Jesus began to teach his disciples: “The Son of Man must suffer much and be rejected by the elders, the chief priests, and the teachers of the Law. He will be put to death, but three days later he will rise to life.” 32He made this very clear to them. So Peter took him aside and began to rebuke him. 33But Jesus turned round, looked at his disciples, and rebuked Peter. “Get away from me, Satan,” he said. “Your thoughts don’t come from God but from human nature!”
34 Then Jesus called the crowd and his disciples to him. “If anyone wants to come with me,” he told them, “he must forget self, carry his cross, and follow me. 35For whoever wants to save his own life will lose it; but whoever loses his life for me and for the gospel will save it. 36Do people gain anything if they win the whole world but lose their life? Of course not! 37There is nothing they can give to regain their life. 38If a person is ashamed of me and of my teaching in this godless and wicked day, then the Son of Man will be ashamed of him when he comes in the glory of his Father with the holy angels.”
Jesus asks the disciples to tell him who they think he is. They believe he is the Messiah - but they don't really know what that implies.
When Peter tries to talk Jesus out of offering himself sacrificially he says "Your thoughts don't come from God but from human nature!" (Verse 33).