And he began to teach them that the Son of Man must suffer many things and be rejected by the elders and the chief priests and the scribes and be killed, and after three days rise again. And he said this plainly. And Peter took him aside and began to rebuke him. But turning and seeing his disciples, he rebuked Peter and said, “Get behind me, Satan! For you are not setting your mind on the things of God, but on the things of man.” (Mark 8:31–33, ESV)
Did you ever find yourself thinking that God had a bad idea? That somehow he didn't get the memo? That he doesn't have his facts straight?
When Jesus broached the idea that he would be cast aside by the Jewish leaders, tried unjustly and murdered, Peter was certain that Jesus was confused. So certain was he that he took God aside and rebuked him. Yes, you read that correctly. Peter attempted to set Jesus straight. The Greek word used means "to express strong disapproval of someone, rebuke, reprove, censure, speak seriously, warn." Basically Peter gave Jesus a good talking to.
But try to understand where Peter was coming from (because we all have a little bit of Peter in us). The one who he came to believe was the Messiah, the one who was supposed to rule and reign and crush the enemies of God and bring in everlasting peace and righteousness (see Isaiah) -- that same Messiah had just plainly told his followers that he was going to die. Peter was having none of that. How could Jesus do all the things he was supposed to do if he was dead?
Peter went off track because he was thinking like a man and not like God (v. 33). He saw through a non-supernatural lens. He took a "God is not sovereign" point of view. He forgot that God's ways are not our ways. It reminds me of John 11 when Mary and Martha were (rightly) devastated in the death of their brother and accused Jesus of not intervening when the opportunity presented itself. But Jesus had something better in mind that a "simple" healing. He was thinking resurrection.
When Jesus interacted with Peter, he wanted Peter to understand that something far greater was going to happen than avoiding death. Jesus was about to make atonement for sin. He was going to shed his blood so that Peter and all who believe could be brought into the family of God. Never forget that you and I will always default to the "thinking like a man" position. When we set our mind on the things of God (Romans 8:5, Colossians 3:2), we enjoy far more peace because we begin to realize that he's up to something bigger and (always) better that what we could imagine. Doing so doesn't mean that we'll figure out what he's up to (Peter still hadn't gotten the whole death and resurrection thing) but it will cause us to rest in his loving arms knowing that he's always working on what is wisest and what is best.