A.T. Robertson Commentary John 3:10

"Jesus answered and said unto him, Art thou the teacher of Israel, and understandest not these things?" — John 3:10 (ASV)

The teacher of Israel (ο διδασκαλος του Ισραηλ). The well-known or the authorized (the accepted) teacher of the Israel of God. Note both articles.

And understandest not these things? (κα ταυτα ου γινωσκεισ; ). After being told by Jesus and after so propitious a start. His Pharisaic theology had made him almost proof against spiritual apprehension. It was outside of his groove (rote, rut, rot, the three terrible r's of mere traditionalism).