Then Peter took him, and began to rebuke him, saying, Be it far from thee, Lord: this shall not be unto thee. -- Matthew 16:22 (KJV)
Matthew marks a turn with "From that time forth." Jesus begins to show His disciples that He must go to Jerusalem "and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day."
Peter objects to the suffering and the killing. He says nothing about "raised again the third day," though it came in the same sentence. He takes Jesus and begins to rebuke Him, calling Him Lord and telling Him no in one breath.
A few verses earlier this same man said, "Thou art the Christ." He was right about who Jesus is. Now he is wrong about what Jesus must do.
An Offence
Jesus turns and says, "Get thee behind me, Satan: thou art an offence unto me: for thou savourest not the things that be of God, but those that be of men."
An offence is a stumbling block, something in the road that trips the one walking it. Jesus has told His disciples where His road goes, and Peter has stepped into the middle of it.
To savour something is to have a taste for it. Peter is minding what men want, and men do not want their Messiah killed. The things of God, this time, include the killing and the rising again. Had Jesus taken Peter's advice, there would have been no third day.
When Obedience Costs
You face Peter's choice when someone you love tells you that obeying God is going to cost them. A friend has decided to confess a wrong nobody else knows about. Your grown son believes God is leading him into work that will pay little. Your first instinct is to offer a way out: wait a year, nobody needs to know, think about your family.
Ask what your advice is protecting. It may be their comfort, or your own.
The next time someone you love tells you what obedience will cost, will your answer sound like Peter's?