Midway through Tabernacles, Jesus begins teaching publicly in the Temple. His hearers marvel: 'How knoweth this man letters, having never learned?' The question concerns recognized education, not basic literacy alone.
Jesus answers by identifying the source of his teaching as the one who sent him.
The Temple courts provided major public spaces for instruction and debate. Advanced Jewish learning was commonly transmitted through teachers and recognized circles of study, so hearers could ask under whom a teacher had learned. The Greek expression about knowing 'letters' can refer to learning or mastery of Scripture rather than simply the ability to read.
John does not identify Jesus as formally trained under a known Jerusalem teacher.
The educational setting clarifies the astonishment. Jesus demonstrates command of sacred teaching without presenting the conventional credentials his audience expects.
His answer also advances John's central claim about authority: he does not compensate by naming an earthly rabbi. He says his teaching comes from the Father who sent him.