Rebuke as Reward: Then he warned them not to tell anyone about him. He began to teach them that the Son of Man must suffer greatly and be rejected by the elders, the chief priests, and the scribes, and be killed, and rise after three days. He spoke this openly… (Mark 7:30-32)
The Greek epitimaō (warn) is a strong word; hardly one of praise and affirmation. Pheme Perkins  has a great insight on what is unfolding: “Readers might expect a word of praise for the confession, since it demonstrates that the disciples are superior to the crowds in their understanding of who Jesus is. Instead, the command to tell no one is introduced with the verb for “rebuke” (ἐπιτιμάω epitimaō), the same verb Mark uses to describe Jesus’ response when the demons acknowledge him as Son of God (3:12). Thus the rebuke does not impugn the correctness of the title being used. The problem with the confession is the inappropriateness of the time (prior to the passion), the context (exorcism and healing miracles), or the witnesses (spoken by demons). Since the episodes surrounding the two affirmations of Jesus’ identity in this section demonstrate that the disciples do not understand that suffering lies at the heart of Jesus’ mission, they are no more able to use the titles “Messiah” and “Son of God” correctly than the demons are. Jesus will accept both titles publicly during his interrogation by the Sanhedrin (Mark 14:62).”
As Perkins notes; it is not that Peter got it wrong, but given that he does not understand and will strongly resist the idea of a suffering Messiah, to that extent he does not understand the unique role Jesus will play in salvation history.
But ever the teacher, Jesus continues in that role to describe what it is that the Messiah must do. Verse 31 marks a new beginning. Prior to this the emphasis has been on Jesus’ authority and power as he cast out demons, healed diseases, commanded the waves, and more. Now the stress will be on his own suffering and death – and the disciples’ responsibility to follow. The lesson is brief and to the point: He began to teach them that the Son of Man must suffer greatly and be rejected by the elders, the chief priests, and the scribes, and be killed, and rise after three days. In its own way, this one verse plays out the remainder of Mark’s gospel. There are four things needed for Jesus to be obedient to his Father’s desire that humanity be redeemed: Jesus must:
- suffer many things,
- be rejected by the religious leaders,
- be killed, and
- after three days rise from the dead.
The beginning of v.32 (sometimes noted as v.32a) is found only in Mark: “He spoke this openly.” Other modern translations have “plainly.” As Mark Twain famously noted: “Many people are bothered by those passages in Scripture which they cannot understand; but as for me, I always noticed that the passages in Scripture which trouble me most are those which I do understand.” Peter understands. He doesn’t like them. Peter would like a Messiah who wouldn’t do a stupid thing like rising from the dead, but a smart thing like never dying (Robert Capon). In what might amount for a tit-for-tat, Peter rebukes Jesus.
Rebuke as Warning: He spoke this openly. Then Peter took him aside and began to rebuke him. At this he turned around and, looking at his disciples, rebuked Peter and said, “Get behind me, Satan. You are thinking not as God does, but as human beings do.” (Mark 7:33-34)
Jesus’ words about the suffering Son of Man sparks a new exchange between Jesus and Peter. As does the previous exchange (vv. 27–30), this episode concludes with a second rebuke (v. 33). Perkins suggests that the second rebuke (v.33) explains the first (v.30) – don’t tell anyone because you still do not understand and continue to think only in human categories. To our modern ear, the moniker “Satan” would seem to equate Pete and the devil himself, but I think that is perhaps too harsh an understanding. One should recall the OT role of satan was as tempter. And just as satan tempted Jesus away from his divine mission in the desert encounter, so too, Peter is tempted Jesus to turn away from the way of the cross. But there is no command to “be gone” only the command to fall in line, in the place of a disciple, behind, following the Master.
The command to “get behind” may also indicate status. Jesus has to come first. Jesus is the leader. Peter when he rebuked Jesus, was putting himself first; so Jesus tells him, “Get behind me!” As Stoffregen notes, when someone suggests that God is their co-pilot, perhaps that is an indication for a need to change places.