December 2

As to your third question Shoghi Effendi would like you to understand that when one believes in One to be divinely inspired and when one is convinced that He has a great mission to the world in His teachings, he must very naturally be ready to accept all that that world-teacher that divinely-inspired Man says. It is with this view that he feels that a real Baha'i would be one who is convinced that Baha'u'llah was a world-teacher and a Messenger of God bearing to mankind a great Message and would therefore be ready to accept all that Baha'u'llah has said and the same is true of the Master, Whom we believe to have been the great propounder of the Baha'i teachings and the One through Whom the Covenant of God was firmly established in the world. 
(From a letter dated 15 February 1926 written on behalf of the Guardian to an individual believer; compilation on scholarship prepared by the Research Department of the Universal House of Justice, 1979)