“Blindness” is referred to specifically seventeen times the gospel of John, all of those occasions in the “book of signs” (chapters 1 – 12) part of the book. Thirteen of the seventeen times it occurs in chapter nine. When you read the chapter, you will understand why.
Up to here, Jesus has performed some magnificent miracles, but this one tops them all: he gives sight to a man born blind. Normal people, seeing the previous signs of Jesus might have no problem believing he was the Christ. But the Jewish leaders (in John, the “Jews” are the Jewish leaders) refuse to believe. They call Jesus a “sinner,” meaning not “someone who sins” but rather a person separated and alienated from God. It does not make sense to the crowds. When quizzed more closely, the formerly blind man takes the leadership to task. “I don’t know who he is, all I know is that he made me see . . . you people claim he is a sinner, but God only listens to the godly. Nobody has ever heard of opening the eyes of a man born blind. If this man were not from God he could do nothing.”
Because the blind man believed in what he saw, the Jewish leadership kicked him out of the synagogue. The implication palpable. Here is a man no longer in fellowship with formal Judaism, but he is in fellowship with God. There must, then, be a disconnect between God and Judaism – at least as promoted by the Jewish leadership.
Remember John’s purpose: to get his readers to keep on trusting in Jesus. As John presents him, Jesus has power over substance, distance, time, resources, natural law, and now, with the healing of the man born blind, misfortune. Who else has such power? What other person with such great power would be willing to help you? If you turn from Jesus, to whom will you turn? Only Jesus has the message of eternal life (6:68). Only Jesus has its power. The only people who cannot see that are those, like the Jewish leadership, who have willingly blinded themselves to the truth.