The two pieces of Jesus’s rebuke of Peter in this week’s gospel to keep in mind are these: 1) Peter is literally out of line—as disciples he’s supposed to be behind Jesus, his rabbi and 2) his attempt to protect Jesus runs counter to the will of God.
The physicality of the moment belies its spiritual depth because Jesus isn’t mad that Peter is questioning his authority or even exercising his own new moral authority. It is how divorced he now is from what God wants.
This is supposed to startle the reader profoundly because in the preceding verses, Peter seems to speak as God. And now, his voice is Satan’s.
Don’t get twisted by literalism here, as Peter becomes misaligned from God in seconds.
Jesus’s corrective, “get behind me,” an instruction to both Peter and Satan, is a stark reminder of order and relationship. Not order for the sake of order. But order that helps clarify and embolden relationship. Which helps keep the disciples aligned with the dream of God.
Peter’s seeming pragmatism, in wanting to protect his rabbi and friend, the very heart of their movement, is very much not what God wants. God has other intentions for the one Peter just called Messiah.
We know this, of course. It isn’t news. But how often are we doing this very thing as Peter does? When we try to protect the church or defend Jesus? There is a whole discipline of apologetics which seeks to rhetorically defend the character and divine vision of Jesus.
Jesus doesn’t just compare Peter to Satan, he seems to speak directly to him in Peter. Remember, it was Satan who sought to cause Jesus to stumble before, to draw him away from his mission by tempting him with power. Now, the temptation is preventing his death. And Jesus recognizes that impulse for what it is.