An interesting post by Chuck Smith about the question of "...Master, who did this sin, this man or his parents, that he was born blind?".
From Chuck Smith...
So the question, "Who did sin, this man or his parents that he was born blind?" Is this God's judgment upon his parents for some sin they did? It is interesting to me that quite often we have that kind of a thought of a direct retribution from God when calamity comes to us. God is punishing me for something that I have done, or something that I did. And thus, this hardship or this difficulty or this painful experience is coming to me as God's judgment upon me because of some wrongdoing. If that were so, I wouldn't be here tonight. You see, if God brought that kind of a direct cause/effect judgment upon people, then God would have to be fair in His justice system. And thus, every person who did the same kind of a deed would have to receive the same kind of a judgment for it. There is not that cause and effect type of judgment at the present time, there will be and God will be just when He judges. Because it will be completely equal judgment. But right now God is seeking to draw men to Himself. And Jesus said, "I didn't come to condemn the world, but that the world through Me might be saved" (John 3:17).
Link for Chuck Smith commentary.