What does John 9:3 mean?

This verse counters a misconception common in Jesus' era, and still part of "eastern" religions today. Jesus' disciples assume that the man they've passed by (John 9:1–2) must be blind as a punishment for something. For them, this raises a difficult question: did the man somehow sin before he was born, or is he being punished for his parents' sin? This suggests the concept of karma, which implies that all suffering in this life is payment, or punishment, for prior acts of wrongdoing.

Jesus' answer clearly and definitively refutes these ideas. In a very broad sense, it's true that all human suffering is the result of sin. Adam's disobedience brought death and destruction to the entire human race (Romans 5:12). It's also true that most of the pain we experience in life is caused by the sin of people—either ourselves or others. Violence, starvation, crime, broken homes, and other effects of sin can impinge on people who are not directly to blame. More specifically, though, Jesus' words prove that not all suffering is punishment for sin. This man, in particular, did not experience blindness as any sort of judgment on sin, either his or someone else's.

A classic interpretation of this verse is the man was born blind specifically so Jesus could perform this miracle. This would harmonize with verses such as 2 Corinthians 12:7–9 and Exodus 4:11. However, it's also true that New Testament Greek was not written using punctuation. Based on the context, it's also possible that Jesus meant His comments about sin and the parents separately from His remarks on the works of God. That is, one could reasonably punctuate this passage as "…or his parents. But, that the works of God might be displayed in him, we must work…" Either way, the emphasis here is refuting that the man's sin was responsible for his condition.