Charles Ellicott Commentary John 9:18

"The Jews therefore did not believe concerning him, that he had been blind, and had received his sight, until they called the parents of him that had received his sight," — John 9:18 (ASV)

But the Jews did not believe.—Better, The Jews therefore did not believe. The words are connected, as an inference, with those which precede. Because of this explanation of the fact, they are driven to the expedient of disbelieving the fact itself. The designation of those who take this position is remarkable. The substantive is not unexpressed, as in John 9:17, nor is it “the Pharisees,” as in John 9:16, but it is the term which we have met with again and again, as marking out the leaders of the Jerusalem party who were opposed to Christ. (Compare to Note on John 1:19.)

Until they called the parents.—After they have done so, they can no longer pretend to doubt the fact (John 9:26). But they hoped that the parents would from fear (John 9:22) have given an answer which would have enabled them to deny the person's identity, or the fact of congenital blindness.