Peter had heard Jesus explaining that he would go to Jerusalem and suffer many things at the hands of the elders, chief priests and teachers of the law, and that he must be killed and on the third day be raised. Peter was upset to hear this, and said to Jesus, “Never, Lord, this shall never happen to you!” (Matt. 16:22)So why was Jesus so upset with Peter to the point where he called him satan, and told Peter to get away from him?
The answer lies in understanding the position of Jesus. Jesus identified himself as the humble servant of God. His intention was to do the will of the Supreme Being. He knew what was going to happen to his body. He knew that he would be making a sacrifice for the Supreme Being: A very painful and tough sacrifice.
There was certainly a great temptation - especially since he knew it would happen - for Jesus to avoid Jerusalem completely and thus avoid having to make this sacrifice and service to the Supreme Being. He could have easily thought of his own comfort and avoided the entire ordeal.
But this was not Jesus’ choice. He understand this was part of his mission. This was part of his service to the Supreme Being. To avoid doing it would be to avoid serving the God that he loved and cared for.
“Out of my sight satan!"We can thus see clearly the meaning of “satan” as defined by Jesus. “Satan” is not a mythological person with a pitch fork who lives in a cave of fire. “Satan” is the intent to please oneself, and the illusory nature of the physical world that responds to that desire. “Satan” is ultimately based upon self-centeredness. “Satan” is the rejection of God's will in lieu of our own will (also referred to as "evil").
This is why, when Jesus was tempted in the desert, he said:
"Away from me, satan! For it is written: 'Worship the Lord your God, and serve Him only.'" (Matt. 4:10)
"You are a stumbling block to me"Because Peter was presenting to Jesus the prospect of going against the will of God, Jesus called him satan. Peter wanted Jesus to avoid the punishment. This made Peter the representative of the temptation to consider the comforts of the body first and avoid the service to God. Jesus confirmed this as he said clearly:
“You do not have in mind the things of God, but the things of men.""The things of men" regards the aspects of the physical world - the world of the physical body and the various issues related to the physical body. Jesus, however, taught that we are not these physical bodies:
"Do not be afraid of those who kill the body but cannot kill the soul." (Matt. 10:28)In other words, Peter's focus was identifying Jesus as the physical body - and not seeing Jesus' loving service relationship with God.
(For a translation of Jesus' statements from the Book of Matthew without institutional sectarian influence, see the Gospels of Jesus - translated from the original Greek texts.)