The Bahá’ís are commanded to establish the oneness of
mankind; if they cannot unite around one point how will they be able to bring
about the unity of mankind?
The purpose of the Blessed Beauty in entering into this
Covenant and Testament was to gather all existent beings around one point so
that the thoughtless souls, who in every cycle and generation have been the
cause of dissension, may not undermine the Cause. He hath, therefore, commanded
that whatever emanateth from the Centre of the Covenant is right and is under
His protection and favour, while all else is error. 
- ‘Abdu’l-Baha  (‘Selections
from the Writings of ‘Abdu’l-Baha’)