What does John 9:10 mean?

Jesus' choice of this particular man for His sixth miraculous "sign" is no accident. In chapter 5, Jesus chose to heal a man who had been crippled for nearly 40 years (John 5:1–9). This meant there could be no doubt about the miraculous nature of the healing. The man would have been known for his condition, and his condition would have been known to be permanent. In this case, the man Jesus healed with muddy clay (John 9:6) had been born blind (John 9:1–2). He was easily recognized by the people of Jerusalem as a beggar (John 9:8). It's the fact that the man is so well-known for being blind that some in the crowd resist believing that he's been cured (John 9:9).

Despite some doubters, most people accept the obvious: this is the same man once known as a blind beggar. Their response question makes perfect sense: "if you're the one who used to be blind, what happened to make you see?" On the other hand, this same question will be repeated no less than four times (John 9:10, 15, 19, 26). These questions assume some kind of natural, mechanical answer. The people are so concerned with those details that they're missing the message of the miracle!

This presents an important perspective on Christian testimony. Through the rest of this chapter, the formerly blind man will be challenged to explain, re-explain, and repeatedly explain his story. Each time, his response is sincere, simple, and honest. What attracts others to his message is not his own charisma, or some deep philosophical idea. People are drawn because they see something powerful and want to know what caused it. The man's answer, consistently, is simply to tell other that it's Jesus who changed his life. Fancy speech and complex ideas are fine, in the right context, but neither are required to spread the "good news" to other people.