john 9:18 But the Jews did not believe concerning him, that he had been blind, and received his sight, until they called the parents of him that had received his sight. - Free Bible Online

      18-23. the Jews did not believe . . . he had been born blind . . . till they called the parents of him that had received his sight--Foiled by the testimony of the young man himself, they hope to throw doubt on the fact by close questioning his parents, who, perceiving the snare laid for them, ingeniously escape it by testifying simply to the identity of their son, and his birth-blindness, leaving it to himself, as a competent witness, to speak as to the cure. They prevaricated, however, in saying they "knew not who had opened his eyes," for "they feared the Jews," who had come to an understanding (probably after what is recorded, Joh 7:50, &c.; but by this time well known), that whoever owned Him as the Christ would be put out of the synagogue--that is, not simply excluded, but excommunicated.

JFB.