Adam Clarke on John 7:15

How knoweth this man letters, having never learned? - The Jewish learning consisted in the knowledge of their own scriptures, and the traditions of their elders. In this learning our blessed Lord excelled. No person ever spoke with more grace and dignity, or knew better how to make a more proper use, or a happier application, of Jewish allegories and parables; because none ever penetrated the sense of the Scriptures as he did; none ever cited them more successfully, or ever showed their accomplishment in so complete and satisfactory a manner. As these branches of learning were taught at the Jewish schools, and our Lord had never attended there, they were astonished to find him excelling in that sort of learning, of which they themselves professed to be the sole teachers.