Teaching is even more difficult than learning … and why is teaching more difficult than learning? Not because the teacher must have a larger store of information, and have it always ready. Teaching is more difficult than learning because what teaching calls for is this: to let learn. The real teacher, in fact, lets nothing else be learned than – learning. His conduct, therefore, often produces the impression that we properly learn nothing from him, if by "learning" we now suddenly understand merely the procurement of useful information. The teacher is ahead of his students in this alone, that he has still far more to learn than they – he has to learn to let them learn. The teacher must be capable of being more teachable than the students. The teacher is far less assured of his ground than those who learn are of theirs. If the relation between the teacher and the taught is genuine, therefore, there is never a place in it for the authority of the know-it-all or the authoritative sway of the official. It still is an exalted matter, then, to become a teacher which is something else entirely than becoming a famous professor.
Heidegger, M. (1968). What is called thinking? (Vol. 8, p. 208). New York: Harper & Row.