John 9:3

3.Neither did this man sin, nor his parents. Christ does not absolutely say that the blind man, and his parents, were free from all blame; but he declares that we ought not to seek the cause of the blindness in sin. And this is what I have already said, that God has sometimes another object in view than to punish the sins of men, when he sends afflictions to them. Consequently, when the causes of afflictions are concealed, we ought to restrain curiosity, that we may neither dishonor God nor be malicious towards our brethren. Wherefore, Christ assigns another reason. This man, he says, was born blind, —

That the works of God might be manifested in him. He does not, say a single work, but uses the plural number, works; for, so long as he was blind, there was exhibited in him a proof of the severity of God, from which others might learn to fear and to humble themselves. It was afterwards followed by the benefit of his cure and deliverance, (257) in which the astonishing goodness of God was strikingly displayed. So then Christ intended, by these words, to excite in his disciples the expectation of a miracle; but at the same time reminds them in a general manner, that this must be abundantly exhibited on the theater of the world, as the true and lawful cause, when God glorifies his name. Nor have men any right to complain of God, when he makes them the instruments of his glory in both ways, whether he shows himself to be merciful or severe.