David O. McKay
In teaching there are three ever-present factors: first, what the teacher is; secondly, what the teacher says; and thirdly, what the teacher does. The least important of these is what the teacher says; the other two are most vital in child training. It is worse folly for a teacher to attempt to teach something which he himself does not believe. There is a sixth sense in most of us, and particularly in children and youth, which instinctively detects the inconsistency between pretension as expressed in words and reality as it exists in thought and feeling. A dishonest teacher cannot effectively teach honesty, nor an athiest teach belief in God, nor an immoral one teach purity of life. True teaching springs from the heart, not from vocal chords.

– David O. McKay