Affiliation with Faith Alone is Insufficient
"So far as non-Bahá'ís affiliating with the Bahá'í Faith is concerned, either a person becomes a Bahá'í and accepts Bahá'u'lláh as the divine Manifestation for this day, or he does not. The tenets of the Bahá'í Faith are simple as outlined by the Guardian, but they do not permit of any variations. In other words, if any members of the ... Movement wish to become Bahá'ís, they will be most welcome; but they can only become Bahá'ís on the basis of accepting Bahá'u'lláh as a divine Manifestation, and of course, with this goes the acceptance of the Bab as the Forerunner, and Abdu'l-Bahá as the Center of the Covenant, and the present Administrative Order.
"When a person has reached the sea of immortality, it is idle to keep seeking elsewhere...."
(From a letter written on behalf of Shoghi Effendi to the Spiritual Assembly of Japan, July 24, 1953: Japan Will Turn Ablaze, pp. 76-77)