The spiritual condition of the Baha'i “teacher” affects the one being taught

The aim is this: The intention of the teacher must be pure, his heart independent, his spirit attracted, his thought at peace, his resolution firm, his magnanimity exalted and in the love of God a shining torch. Should he become as such, his sanctified breath will even affect the rock; otherwise there will be no result whatsoever. As long as a soul is not perfected, how can he efface the defects of others. Unless he is detached from aught else save God, how can he teach severance to others! (‘Abdu’l-Baha, ‘Tablets of the Divine Plan Revealed by 'Abdu'l-Bahá to the North American Bahá'ís’; The Compilation of Compilations, vol. II, Guidelines for Teaching)