One thing is true: although the teacher cannot give the knowledge, he can kindle the light if the oil is in the lamp.

- by Hazrat Inayat Khan

No one can give spiritual knowledge to another, for this is something that is within every heart. What the teacher can do is to kindle the light which is hidden in the heart of the disciple. If the light is not there, it is not the fault of the teacher. There is a verse by Hafiz in which he says, 'However great be the teacher, he is helpless with the one whose heart is closed.' ...
In ancient times, the disciples of the great teachers learned by a quite different method, not an academic method or a way of study. The way was an open heart. With perfect confidence and trust they watched every attitude of the teacher, both towards friends and towards people who looked at him with contempt. They watched their teacher in times of trouble and pain, how he endured it all. They said how patient and wise he had been in discussing with those who did not understand, answering everyone gently in his own language. He showed the mother-spirit, the father-spirit, the brother-spirit, the child-spirit, the friend-spirit, forgiving kindness, an ever-tolerant nature, respect for the aged, compassion for all, the thorough understanding of human nature. This, also, the disciples learned, that no discussion or books on metaphysics can ever teach all the thoughts and philosophy that arise in the heart of man. A person may either study for a thousand years, or he may get to the source and see if he can touch the root of all wisdom and all knowledge. In the center of the emblem of the Sufis there is a heart; it is the sign that from the heart a stream rises, the stream of divine knowledge.