Today's verses are Mark 9:11-13: "And they asked him, 'Why do the scribes say that first Elijah must come?' And he said to them, 'Elijah does come first to restore all things. And how is it written of the Son of Man that he should suffer many things and be treated with contempt? But I tell you that Elijah has come, and they did to him whatever they pleased, as it is written of him.'" Coming down from the Mount of Transfiguration, the disciples asked Jesus about the scribes' teaching that Elijah must come before the Messiah comes (Malachi 4:2). Undoubtedly, they were asking if Elijah's appearance on the mountain was his "coming," as they scribes said must happen. Jesus responded that Elijah must come first "to restore all things," indeed, Elijah had already come in John the Baptist who did restore all things by pointing people to the ultimate Restorer, Jesus.
Jesus then launched into further teaching about how he and John would be treated with contempt "as it is written." He said, "the Son of Man..."should suffer many things and be treated with contempt." Herod and his henchmen had done so to John, "whatever they pleased, as it is written of him."
Jesus saw himself and John in light of Old Testament prophecies that predicted that Messiah would greatly suffer at the hands of men (see Psalm 22:6; Isaiah 53:2; Daniel 9:26; Zechariah 13:7). Jesus saw himself as the fulfillment of prophecies spoken and written hundreds of years before he came. It's a clear claim to deity.
Also, Jesus saw the Old Testament as the Word of God. When he says, "It is written," it begs the question: by whom is it written? The obvious answer is, "God." God wrote it! That's what Jesus is clearly teaching. The Old Testament is God's written and holy Word. Jesus held the written Word of God in high regard. He desired to obey it. He desired to fulfill it in every possible way.
Do you believe, "It is written?" Do you believe the written Word is God's written Word? Do you believe the Bible is God's written Word for all the world? For Jesus, there was no question what he believed.
If you are a follower of Jesus, do you have any option other than to believe what he believed?