“One Who, not only in the Dispensation of Bahá'u'lláh but in the entire field of religious history, fulfills a unique function.”

'Abdu'l-Baha in New York, 1912

An attempt I strongly feel should now be made to clarify our minds regarding the station occupied by Abdu'l-Bahá and the significance of His position in this holy Dispensation. It would be indeed difficult for us, who stand so close to such a tremendous figure and are drawn by the mysterious power of so magnetic a personality, to obtain a clear and exact understanding of the role and character of One Who, not only in the Dispensation of Bahá'u'lláh but in the entire field of religious history, fulfills a unique function. Though moving in a sphere of His own and holding a rank radically different from that of the Author and the Forerunner of the Bahá'í Revelation, He, by virtue of the station ordained for Him through the Covenant of Bahá'u'lláh, forms together with them what may be termed the Three Central Figures of a Faith that stands unapproached  in the world's spiritual history. He towers, in conjunction with them, above the destinies of this infant Faith of God from a level to which no individual or body ministering to its needs after Him, and for no less a period than a full thousand years, can ever hope to rise. 
- Shoghi Effendi  (The World Order of Baha'u'llah)

"Sirru'llah" (the Mystery of God)

'Abdu'l-Baha in front of Memorial Church where He paused during a tour of the Leland Stanford Junior University campus on 8 October 1912 and read the inscription on the stone plaque which reads: "... erected by Jane Stanford to the glory of God and in loving memory of her husband Leland Stanford"

He alone had been accorded the privilege of being called "the Master," an honor from which His Father had strictly excluded all His other sons. Upon Him that loving and unerring Father had chosen to confer the unique title of "Sirru'llah" (the Mystery of God), a designation so appropriate to One Who, though essentially human and holding a station radically and fundamentally different from that occupied by Bahá'u'lláh and His Forerunner, could still claim to be the perfect Exemplar of His Faith, to be endowed with super-human knowledge, and to be regarded as the stainless mirror reflecting His light. 

- Shoghi Effendi  (God Passes By)