This sharp rebuke is found in Mark 8:33 and Matthew 16:23, where Peter tries to dissuade Jesus from His prediction of suffering and death. Jesus responds by saying:

"Get behind me, Satan! For you are not on the side of God, but of man."

In this context, Peter had just confessed that Jesus is the Christ (in Mark 8:29 and Matthew 16:16), but when Jesus began explaining that He must suffer, be rejected and be killed, Peter rebuked Jesus, saying that this should not happen. Jesus' response is a strong rebuke because Peter's words represented a temptation to avoid God's will, which was for Jesus to die for humanity's sins.

Jesus identified this temptation as coming from Satan, as it was an attempt to prevent the fulfillment of God's plan.