A.T. Robertson 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)

The Jews (ο Ιουδαιο). Probably the incredulous and hostile section of the Pharisees in verse 16 (cf. 5:10).

Did not believe (ουκ επιστευσαν). The facts told by the man, "that he had been blind and had received his sight" (οτ ην τυφλος κα ανεβλεψεν), conflicted with their theological views of God and the Sabbath. So they refused belief "until they called the parents" (εως οτου εφωνησαν τους γονεις). Usual construction of εως οτου (= until which time, like εως alone) with aorist active indicative of φωνεω, old verb from φωνη (voice, sound). They called out loud for his parents to throw light on this grave problem to cover up their own stupidity.