From that time Jesus began to show His disciples that He must go to Jerusalem, and suffer many things from the elders and chief priests and scribes, and be killed, and be raised up on the third day. Peter took Him aside and began to rebuke Him, saying, “God forbid it, Lord! This shall never happen to You.” But He turned and said to Peter, “Get behind Me, Satan! You are a stumbling block to Me; for you are not setting your mind on God’s interests, but man’s.” (Matthew 16:21-23, NASB)
This account is from Apostle Matthew. He was an eye witness as Jesus began to prepare the disciples for what was about to take place, His arrest, torture, crucifixion, and resurrection. Other Gospel accounts speak of the apostles’ grief, or their failure to understand. But Matthew’s story tells of Simon Peter’s “rebuke,” and Jesus’ declaration that Peter was a “stumbling block.”
Jesus’ prophecy of His own coming demise must have been hard to understand. He had been telling the disciples that He was the Son of God. He had performed miracles and healed the sick and the crippled. How could the authorities arrest this Man and put Him to death? And what was this about being “raised up on the third day”?
Peter to the rescue! He wouldn’t let the prediction of Jesus’ demise come true. He, along with the Zebedee brothers, was part of Jesus’ inner circle. He would be Jesus’ bodyguard. Jesus would have nothing to worry about. He would talk some sense into Jesus, straighten Him out. What could go wrong? Wait, what?

“Get Behind Me Satan.” Found at Catholic for Life, https://www.catholicforlife.com/tag/get-behind-me-satan/
Satan? Jesus rebuked Peter’s rebuke by calling him “Satan.” “A stumbling block.” That he was “not setting [his] mind on God’s interests, but man’s.” Many of Israel’s people were looking for a political Messiah Who would expel the Roman occupiers and rule Israel with justice. The disciples, despite all the time they spent with Jesus, didn’t comprehend what this was all about. Jesus didn’t come to the earth He created to free them from Rome, He came to free them from their sins. To do that, He had to go to Jerusalem, and present Himself as the Lamb of God, a sacrifice acceptable to God the Father.
Imagine how Peter felt at Jesus’ rebuke. Not long before this, during a discussion about Who Jesus is, he had confessed that Jesus is “the Christ, the Son of the living God.” (Matthew 16:16) Jesus praised him, and was ready to hand him the keys to the kingdom of heaven. Now the Christ was calling him “Satan”! Did Peter have a demon? I don’t know. Perhaps Jesus was giving him a wake-up call. After all, He had The Plan, The Big Picture, and He wanted Peter on board.
Ever since Adam and Eve sinned in the Garden of Eden, God had a plan of redemption to bring men and women back to peace with Him. He would eventually send His Son to earth, and He would act as a sacrifice. He would take the punishment we deserve as a substitute for our salvation. We deserve to die for our sins. Jesus paid the price for us. Our part is to accept His sacrifice, and ask Jesus into our hearts.