“the first stirrings of God’s Revelation within His [Bahá’u’lláh’s] soul” while in the Siyáh-hál

“One night in a dream,” He Himself, calling to mind, in the evening of His life, the first stirrings of God’s Revelation within His soul, has written, “these exalted words were heard on every side: ‘Verily, We shall render Thee victorious by Thyself and by Thy pen. Grieve Thou not for that which hath befallen Thee, neither be Thou afraid, for Thou art in safety. Ere long will God raise up the treasures of the earth—men who will aid Thee through Thyself and through Thy Name, wherewith God hath revived the hearts of such as have recognized Him.’” 

- Shoghi Effendi  (God Passes By, chapter 6)

Conditions under which a “Revelation, hailed as the promise and crowning glory of past ages and centuries” was born

A Revelation, hailed as the promise and crowning glory of past ages and centuries, as the consummation of all the Dispensations within the Adamic Cycle, inaugurating an era of at least a thousand years’ duration, and a cycle destined to last no less than five thousand centuries, signalizing the end of the Prophetic Era and the beginning of the Era of Fulfillment, unsurpassed alike in the duration of its Author’s ministry and the fecundity and splendor of His mission—such a Revelation was, as already noted, born amidst the darkness of a subterranean dungeon in Tihrán—an abominable pit that had once served as a reservoir of water for one of the public baths of the city. Wrapped in its stygian gloom, breathing its fetid air, numbed by its humid and icy atmosphere, His feet in stocks, His neck weighed down by a mighty chain, surrounded by criminals and miscreants of the worst order, oppressed by the consciousness of the terrible blot that had stained the fair name of His beloved Faith, painfully aware of the dire distress that had overtaken its champions, and of the grave dangers that faced the remnant of its followers—at so critical an hour and under such appalling circumstances the “Most Great Spirit,” as designated by Himself, and symbolized in the Zoroastrian, the Mosaic, the Christian, and Muhammadan Dispensations by the Sacred Fire, the Burning Bush, the Dove and the Angel Gabriel respectively, descended upon, and revealed itself, personated by a “Maiden,” to the agonized soul of Bahá’u’lláh. 

- Shoghi Effendi  ('God Passes By', chapter 6)

Bahá’u’lláh’s Revelation in relation to “all the Dispensations gone before it”

In conclusion of this theme, I feel, it should be stated that the Revelation identified with Bahá’u’lláh

• abrogates unconditionally all the Dispensations gone before it,
• upholds uncompromisingly the eternal verities they enshrine,
• recognizes firmly and absolutely the Divine origin of their Authors,
• preserves inviolate the sanctity of their authentic Scriptures,
• disclaims any intention of lowering the status of their Founders or of abating the spiritual ideals they inculcate,
• clarifies and correlates their functions,
• reaffirms their common, their unchangeable and fundamental purpose,
• reconciles their seemingly divergent claims and doctrines,
• readily and gratefully recognizes their respective contributions to the gradual unfoldment of one Divine Revelation,
• unhesitatingly acknowledges itself to be but one link in the chain of continually progressive Revelations,
• supplements their teachings with such laws and ordinances as conform to the imperative needs, and are dictated by the growing receptivity, of a fast evolving and constantly changing society,
• and proclaims its readiness and ability to fuse and incorporate the contending sects and factions into which they have fallen into a universal Fellowship, functioning within the framework, and in accordance with the precepts, of a divinely conceived, a world-unifying, a world-redeeming Order. 

- Shoghi Effendi  (God Passes By, chapter 6)

Impossible to “attempt an exhaustive survey of the prophetic references to Bahá’u’lláh’s Revelation”

To attempt an exhaustive survey of the prophetic references to Bahá’u’lláh’s Revelation would indeed be an impossible task. To this the pen of Bahá’u’lláh Himself bears witness: “All the Divine Books and Scriptures have predicted and announced unto men the advent of the Most Great Revelation. None can adequately recount the verses recorded in the Books of former ages which forecast this supreme Bounty, this most mighty Bestowal.” 

- Shoghi Effendi  (God Passes By, chapter 6)

“‘Abdu’l‑Bahá’s…tribute to the transcendent character of the Revelation” of Bahá’u’lláh”

And last but not least is ‘Abdu’l‑Bahá’s own tribute to the transcendent character of the Revelation identified with His Father:

• “Centuries, nay ages, must pass away, ere the Day-Star of Truth shineth again in its mid-summer splendor, or appeareth once more in the radiance of its vernal glory.”
• “The mere contemplation of the Dispensation inaugurated by the Blessed Beauty,” He furthermore affirms, “would have sufficed to overwhelm the saints of bygone ages—saints who longed to partake for one moment of its great glory.”
• “Concerning the Manifestations that will come down in the future ‘in the shadows of the clouds,’ know verily,” is His significant statement, “that in so far as their relation to the source of their inspiration is concerned they are under the shadow of the Ancient Beauty. In their relation, however, to the age in which they appear, each and every one of them ‘doeth whatsoever He willeth.’”
• And finally stands this, His illuminating explanation, setting forth conclusively the true relationship between the Revelation of Bahá’u’lláh and that of the Báb: “The Revelation of the Báb may be likened to the sun, its station corresponding to the first sign of the Zodiac—the sign Aries—which the sun enters at the vernal equinox. The station of Bahá’u’lláh’s Revelation, on the other hand, is represented by the sign Leo, the sun’s mid-summer and highest station. By this is meant that this holy Dispensation is illumined with the light of the Sun of Truth shining from its most exalted station, and in the plenitude of its resplendency, its heat and glory.” 

- Shoghi Effendi  ('God Passes By', chapter 6)