After Lord Jesus had been acknowledged by Peter to be the Messiah and the Son of God (Matt. 16:16), days before, now he was rebuked by the same Jesus who blessed him and changed his name into ‘Stone’ (Petros) due to his valiant declaration of faith, which in itself became the ‘Rock’ (Petra) and the whole basis of our salvation, acknowledging Jesus for whom He claims to be, and to submit to Him under that conviction.
Lord Jesus started to speak clearly about his future immolation, preparing his disciples in advance. But Peter, in a very human way, moved by his love for our Lord, he told Jesus that that should never happen to Him, insinuating probably, like when he cut Malchus’ ear during our Lord’s arrest (Jn 18:10), an armed violent resistance to it.
Jesus, who knew that this could not be avoided (Matt 26:54), rebuked Peter by saying the harsh words:
“Get behind me, Satan!”
Because even though Simon-Peter was moved by his love for our Lord, he paid no attention to God’s greater plan of salvation, and therefore, became automatically, a practical obstacle to God’s will. An indirect instrument of Satan who wanted to destroy God’s plan of human redemption.
From here, we learned that Jesus rebuked Peter for this lack of faith and spiritual vision, and not for being under direct influence of the devil. The devil itself did not believe that Jesus’s death on the cross would redeem the world, because he ignored that He was divine and the value of his atoning sacrifice. Satan viewed Jesus’s death as another human death.
Peter, surprised by our Lord’s answer, motivated Jesus to explain to his disciples, about taking their ‘Cross’ and the sacrifice that would mean to be a disciple, in the next verses.