"Then He came to Bethsaida; and they brought a blind man to Him, and begged Him to touch him. So He took the blind man by the hand and led him out of the town. And when He had spit on his eyes and put His hands on him, He asked him if he saw anything.
And he looked up and said, 'I see men like trees, walking.'
Then He put His hands on his eyes again and made him look up. And he was restored and saw everyone clearly. Then He sent him away to his house, saying, 'Neither go into the town, nor tell anyone in the town.' " (Mark 8:22-26)
Jesus spits on the man's eyes, which only partially restores his sight, and then he lays hands on him again, which finally heals him completely. Jesus heals dozens of people in the gospels, but this is the only case where he fails on the first try. Why should the perfect Son of God need two tries to heal a man? I have no idea—and as it turns out, I'm not the only one.
|A useful visualization.|
For the few passages in Mark that contain completely unique content, the reason for their omission from Matthew and Luke is often quite evident. In one, Mark 3:20-21, those around Jesus think he's out of his mind—a rather embarrassing detail that the later authors would be eager to get rid of. The reason for removing the Parable of the Growing Seed is less clear; perhaps they thought its message was more muddled than that of the similar yet better-crafted Parable of the Sower. Finally there's the "Long Ending" of Mark, which is widely thought to be a forgery that was added later.
So it's no big surprise, then, that both of the later synoptic authors made a deliberate decision to remove the "blind man of Bethsaida" story from their gospels, while using all of the material surrounding it. They realized that this passage is totally inconsistent with the power that Jesus displays in the other gospel tales. Jesus making mistakes wasn't a big deal for the earliest Christians, who saw him merely as a messianic prophet. But as Jesus became increasingly exalted in Christianity (see my Jesus, Interrupted posts for more on that), the gospel writers were compelled to modify their stories accordingly. So went the very human process of editing a very human book.