John Gill Commentary John 9:10

"They said therefore unto him, How then were thine eyes opened?" — John 9:10 (ASV)

Therefore said they to him
When the case was clear, and it was out of question that he was the man:

how were your eyes opened ?
or made to see: they might well ask this question, since such a thing was never known before, that one born blind received his sight; and as great a miracle it is in grace, and as great a mystery to a natural man, how one should be born again, or be spiritually enlightened.