What does Mark 9:12 mean?
Malachi 4:6 promises that Elijah will return before the day of the Lord to reconcile relationships in Israel. "Elijah," in the form of John the Baptist, did come with the intent to "restore all things." That was his mission, but hardened hearts rejected his message of repentance and arranged for his murder, instead. Elijah, too, was persecuted by King Ahab and Queen Jezebel (1 Kings 19). While the disciples dream of glory, Jesus draws them back to the hardships God's prophets went through, tying it into His own future suffering.When Jesus calls Himself "the Son of Man," He is referring to the figure in Daniel to whom is given an everlasting dominion over the world (Daniel 7:13–14). The disciples can't understand how this position of power, granted by the Ancient of Days, has anything to do with someone who will be abused and killed by Jewish leadership. Jesus gives them a subtle clue by paraphrasing Isaiah 53:3 from the passage on the Suffering Servant: "He was despised and rejected by men, a man of sorrows and acquainted with grief; and as one from whom men hide their faces he was despised, and we esteemed him not." What they don't yet understand is that the church age must come before God can finish with Israel.
God explains the timeline in the prophecy of the "70 weeks" (Daniel 9:24–27). The 70 weeks are seventy groups of seven years that outline the fate of Israel from the time Cyrus declares that the Israelites may return to Jerusalem (Ezra 1:2–4) until the end of the tribulation. At the point of the sixty-ninth week, "an anointed one shall be cut off and shall have nothing" (Daniel 9:26). This is Jesus in His role as the Suffering Servant (Isaiah 53). Both prophecies refer to Jesus' crucifixion, but the idea that God's chosen one, the Messiah, will suffer and die does not fit into the theology of Judaism, either then or today.
Daniel's 70 weeks are all about Israel, but they are not contiguous. Between the sixty-ninth and seventieth week is the church age: when the gospel will go to the Gentiles. Although the disciples are promised leadership positions in Jesus' more literal reign, their important work is in establishing the church. It is also in this time that they will face their own hardships and pick up their own crosses (Mark 8:34–35).