He (the Self) of whom many are not even able to hear, whom many, even when they hear of him, do not comprehend; wonderful is a man, when found, who is able to teach him (the Self); wonderful is he who comprehends him, when taught by an able teacher.

In plain words: Many people never even hear about the Self, the true inner being in each of us. Many who hear about it still do not understand. A person who can teach it is rare and wonderful, and so is a person who understands it.