So Peter is a fisherman, a dude, Jesus’ sidekick and the recent winner of the name-that-king-of-kings contest.
Mark 8:31-33 (NIV)
He then began to teach them that the Son of Man must suffer many things and be rejected by the elders, chief priests and teachers of the law, and that he must be killed and after three days rise again.  He spoke plainly about this, and Peter took him aside and began to rebuke him.  But when Jesus turned and looked at his disciples, he rebuked Peter. “Get behind me, Satan!” he said. “You do not have in mind the things of God, but the things of men.”
Things often do not go according to our plans, but few things were going to look more disastrous than the impending crucifixion. Peter said, naw! Can’t be! And Jesus cuts to the truth fast–you gotta see God’s plan.
Nothing takes more faith than believing an obscure Israeli construction worker can save you by dying.
The things of God–mysterious, often dazzling hard to watch. But absolute game changers.