At this point in Jesus’ ministry, he has demonstrated to his disciples repeatedly who he is. Most recently, he fed a crowd of 5,000 men with 5 loaves of bread and then walked on the Sea of Galilee. In chapter sixteen, Jesus asks his disciples if they understand who he is. Peter correctly answers that Jesus is the Messiah who fulfills all the OT prophecies.
Starting in verse 21, however, Jesus reveals to his disciples, for the first time, where his ministry is ultimately leading. He will go to Jerusalem, be tortured and killed, and then be raised from the dead three days later. Verse 21 effectively introduces the rest of Matthew’s Gospel, because all of the following text will focus on the road to the cross.
Peter, the very disciple who just correctly identified Jesus, then takes Jesus aside and rebukes him! Peter tells Jesus that Jesus must be wrong about his suffering and dying at the instigation of the Jewish leadership in Jerusalem. In Peter’s mind, the Messiah should not suffer at all, but immediately start his glorious reign. Jesus responds to Peter by telling him that Peter is playing the role of the devil, for the devil does not want Jesus to accomplish his mission. Satan had already tempted Jesus in chapter four by offering him power over the entire earth. He could skip the suffering and death of the cross; all Jesus would have to do would be to worship Satan.
In a similar way, Peter is trying to convince Jesus to inaugurate his messianic kingdom, but without going to the cross. Peter’s desire for Jesus is directly counter to God’s plan. Peter has become a stumbling block to God’s plan.
In verses 24-26, Jesus teaches the disciples that following him (doing the will of God) will entail suffering and perhaps even death (this is the meaning of “taking up your cross”). And, in fact, according to church tradition, all of Jesus’ closest disciples would die as martyrs, except for John. The reward for suffering and possibly dying for Jesus is eternal life. Without gaining eternal life, this earthly life is pointless. The wealthiest person has gained nothing if she hasn’t dedicated her life to Jesus.
But why should followers of Jesus accept suffering in this life? Because Jesus is going to return to earth and judge everyone for the choices they made during their lives. Those who chose to faithfully follow Jesus will be rewarded according to their deeds. Those who chose to reject Jesus will be judged according to their deeds. Therefore, the person who suffers greatly for Jesus on earth will be more than compensated when the Messiah begins his future reign.
Many Christians are surprised that all people will judged for their deeds at the inauguration of the messianic kingdom, but this idea is clearly taught throughout Scripture (see Ps 62:12; Prov 24:12; Rom 2:6; 2 Cor 11:15; Rev 22:12). When Jesus speaks of himself as being the judge of all mankind, he is likely alluding to Daniel 7:13-14 and applying all of the OT passages on divine judgment to himself.
Jesus then reassures his disciples that some of them will receive amazing confirmation of his Messiahship before they die. That confirmation would come one week later for Peter, James, and John, Jesus’ inner circle. Jesus takes them up to the top of a mountain and before their very eyes he is transformed. “[H]is face shone like the sun, and his clothes became white as light.” Recall how Moses’ face shone with glory after his encounter with God in Exodus 34. Not only that, but Moses and Elijah are standing there speaking to him!
What does the presence of Moses and Elijah signify? Craig Blomberg, in vol. 22, Matthew, The New American Commentary writes:
they were key representatives of the law and prophets [or, the entire Old Testament], they lived through the two major periods of Old Testament miracles, they were key messianic forerunners whose return was often expected with the advent of the Messiah, and they were often believed never to have died but to have gone directly to God’s presence (2 Kgs 2:1–12 makes this clear with reference to Elijah; in the case of Moses the belief is based more on intertestamental literature like the Assumption of Moses).
Michael Wilkins, in The Gospels and Acts (The Holman Apologetics Commentary on the Bible), further elaborates on the presence of Moses and Elijah:
They represent the Law and the Prophets witnessing to Jesus as the Messiah who fulfills the OT (cf. 5: 17) and who has the eschatological role of initiating the kingdom of God (4: 17). Moses was considered the model prophet (Deut 18: 18) and Elijah the forerunner of Messiah (Mal 4: 5– 6; cf. Matt 3: 1– 3; 11: 7– 10). Both had visions of the glory of God on a mountain— Moses on Mount Sinai (Exod 24: 15) and Elijah on Mount Horeb (1 Kgs 19: 8).
Peter’s first reaction is to figure out a way to get Moses and Elijah to stay, so he offers to build shelters for Jesus, Moses, and Elijah. But Peter is cut off when a bright cloud overshadows them and a voice booms out, “This is my beloved Son, with whom I am well pleased; listen to him.” God the Father repeats the same words He spoke when Jesus was baptized by John the Baptist, but He adds “Listen to him” to emphasize to Peter, James, and John that they are not to question his road to the cross. It is the road Jesus must take.
Blomberg reminds us how the cloud is connected to the God of the Old Testament:
The cloud reminds us of the one that overshadowed Moses on Sinai, leading to his dazzling splendor when he descended from the mountain (Exod 34:29–35, on which cf. also Paul’s remarks in 2 Cor 3:7–18), the cloud that enveloped the tabernacle when God’s glory filled it (Exod 40:34), and the cloud that followed the Israelites by day throughout their wilderness wanderings (Exod 40:36–38).
After the disciples fall on their faces in terror from hearing the voice of God, Jesus tells them to rise and not be afraid. When they arise, Elijah and Moses are gone. Jesus is standing there alone. Blomberg adds, “The disciples must focus on Christ alone. He will prove sufficient for their needs.”