A.T. Robertson Commentary John 9:30

"The man answered and said unto them, Why, herein is the marvel, that ye know not whence he is, and [yet] he opened mine eyes." — John 9:30 (ASV)

Why, herein is the marvel (εν τουτω γαρ το θαυμαστον εστιν). This use of γαρ (γε + αρα, accordingly indeed) to bring out an affirmation from the previous words is common enough. "Why in this very point is the wonder" (θαυμαστον, old verbal adjective from θαυμαζω as in Mt 21:42). The man is angry now and quick in his insight and reply. You confess your ignorance of whence he is, ye who know everything, "and yet (adversative use of κα again) he opened my eyes" (κα ηνοιξεν μου τους οφθαλμους). That stubborn fact stands.