John 9:2 - Albert Barnes' Notes on the Bible

Master, who did sin? ... - It was a universal opinion among the Jews that calamities of all kinds were the effects of sin. See the notes at Luke 13:1-4. The case, however, of this man was that of one that was blind from his birth, and it was a question which the disciples could not determine whether it was his fault or that of his parents. Many of the Jews, as it appears from their writings (see Lightfoot), believed in the doctrine of the transmigration of souls; or that the soul of a man, in consequence of sin, might be compelled to pass into other bodies, and be punished there. They also believed that an infant might sin before it was born (see Lightfoot), and that consequently this blindness might have come upon the child as a consequence of that. It was also a doctrine with many that the crime of the parent might be the cause of deformity in the child, particularly the violation of the command in Leviticus 20:18.