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.

Knoweth this man letters - The Jewish letters or science consisted in the knowledge of their Scriptures and traditions. Jesus exhibited in his discourses such a profound acquaintance with the Old Testament as to excite their amazement and admiration.

Having never learned - The Jews taught their law and tradition in celebrated schools. As Jesus had not been instructed in those schools, they were amazed at his learning. What early human teaching the Saviour had we have no means of ascertaining, further than that it was customary for the Jews to teach their children to read the Scriptures. 2 Timothy 3:15; "from a child thou (Timothy) hast known the holy scriptures."

7:15 How does this man know letters, having never learned? - How comes he to be so well acquainted with sacred literature as to be able thus to expound the Scripture, with such propriety and gracefulness, seeing he has never learned this, at any place of education?