When Jesus heard that they had thrown him out, He found the man and said, “Do you believe in the Son of Man?”
To recap what has happened to this man, he was born blind. Jesus’s disciples see him and ask Jesus whose sin caused the blindness. Jesus says he was born blind that God would be glorified, and He healed him. This happened to be on the Sabbath, so the Pharisees got involved. After much questioning, the man ends up arguing that whoever healed him must come from God, and he gets thrown out of the synagogue. Here Jesus finds him.
Although no one’s sin caused this blindness, Jesus shows us that blindness is a metaphor for sin. Jesus came to heal the blind (forgive the sinner) and make the seeing blind (reveal the sinfulness of the self-righteous). When the Pharisees ask if He is calling them blind, He says that because they claim to see (to be righteous), they are blind (sinners). He actually says that their guilt remains.
This blind man was a more reliable witness to who Jesus was than the Bible scholars who were supposed to know. Back in the synagogue, when the Pharisees were grilling him, all he could say was, “Whether He is a sinner I do not know. There is one thing I do know: I was blind, but now I see!” (John 9:25). Case closed.