Jesus turned and said to Peter, "Get behind me, Satan! You are an obstacle to me. You are thinking not as God does, but as human beings do."
Gospel's Commentary
Today Jesus responds very strongly to Simon Peter. What a reprimand! A few seconds earlier, Peter has declared that Jesus is the Son of God and, in turn, Christ bestows on him the primacy of the Church (he is the first Pope!). But Jesus, speaking to them confidentially, adds that He will be executed... Simon refuses to accept the Passion of the Lord: "No such thing shall ever happen to you"
—Peter is thinking like a simple "company manager"... and he has become a slave to success. But God is God and His logic is just another one: His success is "surrendering for love".