John 3:10

σὺ εἶ ὁ διδάσκ. Art thou the teacher, a representative of the highest knowledge and supreme authority in the Church? Jesus is astonished at the ignorance of Rabbis, just as He marvelled at the unbelief of His countrymen (Mark 6:6). Ἰσραήλ, frequent in Matt., Luke, and Acts, occurs only 4 times in S. John (John 1:31; John 1:50; John 13:13, and here): ‘the chosen people’ is the idea conveyed. Οὐ γινώσκεις. Perceivest not: this was knowledge which he might have acquired, had he made the effort. Winer, p. 143.