Teach ye the Cause of God, O people of Bahá

Teach ye the Cause of God, O people of Bahá, for God hath prescribed unto every one the duty of proclaiming His Message, and regardeth it as the most meritorious of all deeds.

-Baha'u'llah in Gleanings

http://www.ibiblio.org/Bahai/Texts/EN/GWB/GWB-128-printable.html

God hath prescribed unto every one the duty of teaching His Cause. Whoever ariseth to discharge this duty, must needs, ere he proclaimeth His Message, adorn himself with the ornament of an upright and praiseworthy character, so that his words may attract the hearts of such as are receptive to his call. Without it, he can never hope to influence his hearers. 

-Baha'u'llah in Gleanings

http://reference.bahai.org/en/t/b/GWB/gwb-158.html