Albert Barnes Commentary John 9:3

"Jesus answered, Neither did this man sin, nor his parents: but that the works of God should be made manifest in him." — John 9:3 (ASV)

Neither hath this man sinned, etc. That is, his blindness is not the effect of his sin, or that of his parents. Jesus did not, evidently, mean to affirm that he or his parents were without any sin, but that this blindness was not the effect of sin. This answer is to be interpreted by the nature of the question submitted to him. The sense is, "his blindness is not to be traced to any fault of his or of his parents."

But that the works of God. This thing has happened so that it might appear how great and wonderful are the works of God. By the works of God, here, is evidently intended the miraculous power which God would put forth to heal the man, or rather, perhaps, the whole that happened to him in the course of divine providence—first his blindness, as an act of his providence, and then his healing him, as an act of mercy and power. It has all happened, not by the fault of his parents or of himself, but by the wise arrangement of God, so that it might be seen in what way calamities come, and in what way God meets and relieves them. And from this we may learn:

1. To pity and not to despise and blame those who are afflicted with any natural deformity or calamity. While the Jews regarded it as the effect of sin, they looked upon it without compassion. Jesus tells us that it is not the fault of man, but proceeds from the wise arrangement of God.
2. All suffering in the world is not the effect of sin. In this case it is expressly so declared; and there may be many modes of suffering that cannot be traced to any particular transgression. We should be cautious, therefore, in affirming that there can be no calamity in the universe but by transgression.
3. We see the wise and wonderful arrangement of Divine Providence. It is a part of his great plan to adapt his mercies to human woes; and often calamity, want, poverty, and sickness are permitted, so that he may show the provisions of his mercy, so that he may teach us to prize his blessings, and so that deep-felt gratitude for deliverance may bind us to him.
4. Those who are afflicted with blindness, deafness, or any deformity, should be submissive to God. It is his appointment, and is right and best. God does no wrong, and the universe will, when all his works are seen, feel and know that he is just.