Reading this Sunday’s Gospel as the back half of last Sunday’s Gospel (which it is), Peter is first praised and then condemned by Jesus. It all happens so fast (with Peter going from “keys of the kingdom” to “get behind me, Satan” in less than 4.0 verses), that it’s easy to miss why it happens.
In last Sunday’s Gospel, Peter blurts out that Jesus is "the Christ, the son of God," and Jesus is overjoyed. Jesus is the Christ, the Messiah, and Peter gets it. Only, as this Sunday’s Gospel shows, Peter doesn’t really get it.
People in Jesus’ time expected the Messiah to be a military leader, sent by God to throw out the Romans and restore their independence. Peter was no different, which is why - when Jesus started to explain how he would suffer - Peter took Jesus aside. That isn’t what the Messiah does…only it is, and you can almost hear Jesus facepalm as Peter gets going with his rebuke.
Knowing how the whole story plays out, it’s easy to laugh at Peter getting smacked down by Jesus. When we hear Sunday’s Gospel, we need to keep in mind our own (spoken and unspoken) expectations for Jesus, and remember that Jeremiah is more of a model than anything we might want or imagine. We can be more like Peter than we might want to admit.
Sunday's Readings: http://www.usccb.org/bible/readings/083114.cfm