This was the man who just said to Jesus, "You are the Messiah." Peter took Him aside. The indication is that it was something done in urgency, that there was a deep feeling and perhaps even a bit of jostling. I don't mean that it was done meanly at all.
Peter clearly believed that Jesus was the Messiah. But what was wrong here? Peter also disagreed with the way the purpose of God was going to be worked out through Christ. What Peter objected to was his good Friend having to go through a scourging, a painful and shameful crucifixion, which is a terrible way to die, especially for one so good. Peter knew that. For Jesus to suffer all the ignominy; to have Him berated by those who were in authority—and Peter recognized that those people who were in the seats of authority couldn't hold a candle to Jesus. And yet these mean men would be sitting in a place where they could actually have Him delivered to death.
Peter disagreed with what the Messiah said God's purpose was and how it was going to be worked out. I think we can relate to what Peter said. It really was a touching sentiment, because he didn't want to see Christ suffer and die; but brethren, the sentiment was wrong and Christ identified the source of what Peter said as Satan.
Now how? How did He isolate that and say this was from Satan? One way was because it followed the same pattern as Satan's temptations in Matthew 4—offering Christ Messiahship without suffering. That's what he offered Him. "Just bow down to me and I'll give you all the kingdoms of the world. You don't have to suffer, Jesus." (That last statement of mine was implied.)
Satan knew the scriptures. He knew who Jesus was and he also knew the scriptures better than Peter did. Satan was tossing in front of Christ the temptation of achieving Messiahship, rulership over the world, without having to go through the ignominy of a scourging and death by crucifixion.
I'm sure it was quite a temptation. Probably most of us would not have taken that way. Jesus recognized it right away.
We know that was not God's will. God's will was that the Messiah first had to suffer and die for man's sins. Where does it say that in God's word? Isaiah 52 and 53 are very clear. That's what God's will was regarding the Messiah.
Peter, when he spoke, was not speaking God's words or thoughts regarding the Messiah. Instead, Peter was speaking—he was mouthing—what he would like to see. But God's thoughts are not man's thoughts. What Peter was speaking was the common Jewish conception of a warrior messiah who would put down the enemies of Judah, elevate Judah over their conquerors, and Judah would become the kingpin of all the nations on the earth. Thus, the suffering Messiah, who dies for the sins of man, would be by-passed. But God had willed first things first.
Where in the world did Peter get that idea? (Here comes Satan back into the picture again.) Peter was a victim of disinformation regarding God's word and he became a stumbling block to others. The disinformation came from Satan through his false prophets.