Bahá’u’lláh “decided…to retire”: - “these showers of afflictions and unceasing calamities”

In the early days of Our arrival in this land, [Iraq] when We discerned the signs of impending events, We decided, ere they happened, to retire. We betook Ourselves to the wilderness, and there, separated and alone, led for two years a life of complete solitude. From Our eyes there rained tears of anguish, and in Our bleeding heart there surged an ocean of agonizing pain. Many a night We had no food for sustenance, and many a day Our body found no rest. By Him Who hath My being between His hands! notwithstanding these showers of afflictions and unceasing calamities, Our soul was wrapt in blissful joy, and Our whole being evinced an ineffable gladness. 

- Baha’u’llah (‘The Kitab-i-Iqan’)

Bahá’u’lláh’s overwhelming suffering: - Mírzá Áqá Ján’s testimony: “Blessed Beauty evinced such sadness that the limbs of my body trembled”

Mírzá Áqá Ján himself has testified: “That Blessed Beauty evinced such sadness that the limbs of my body trembled.” He has, likewise, related, as reported by Nabil in his narrative, that, shortly before Bahá'u'lláh's retirement, he had on one occasion seen Him, between dawn and sunrise, suddenly come out from His house, His night-cap still on His head, showing such signs of perturbation that he was powerless to gaze into His face, and while walking, angrily remark:

"These creatures are the same creatures who for three thousand years have worshipped idols, and bowed down before the Golden Calf. Now, too, they are fit for nothing better. What relation can there be between this people and Him Who is the Countenance of Glory? What ties can bind them to the One Who is the supreme embodiment of all that is lovable?”

“I stood,' declared Mírzá Áqâ Ján, “rooted to the spot, lifeless, dried up as a dead tree, ready to fall under the impact of the stunning power of His words. Finally, He said:

"Bid them recite: “Is there any Remover of difficulties save God? Say: Praised be God! He is God! All are His servants, and all abide by His bidding!” Tell them to repeat it five hundred times, nay, a thousand times, by day and by night, sleeping and waking, that haply the Countenance of Glory may be unveiled to their eyes, and tiers of light descend upon them." He Himself, I was subsequently informed, recited this same verse, His face betraying the utmost sadness. ...

“Several times during those days, He was heard to remark: ’We have, for a while, tarried amongst this people, and failed to discern the slightest response on their part.’ Oftentimes He alluded to His disappearance from our midst, yet none of us understood His meaning.” 

- Shoghi Effendi (‘God Passes By’)

Bahá’u’lláh’s overwhelming suffering: - “until the present day, such malice, envy and hate have in no wise appeared, nor will they ever be witnessed in the future”

“In these days,” He, describing in the Kitáb-i-Íqán the virulence of the jealousy which, at that time, was beginning to bare its venomous fangs, has written, “such odors of jealousy are diffused, that … from the beginning of the foundation of the world … until the present day, such malice, envy and hate have in no wise appeared, nor will they ever be witnessed in the future.” 

- Shoghi Effendi (‘God Passes By’)

Bahá’u’lláh’s overwhelming suffering: - “Noah’s flood is but the measure of the tears I have shed…”

Furthermore, in His Qasídiy-i-Varqá’íyyih, an ode revealed during the days of His retirement to the mountains of Kurdistán, in praise of the Maiden personifying the Spirit of God recently descended upon Him, He thus gives vent to the agonies of His sorrow-laden heart: “Noah’s flood is but the measure of the tears I have shed, and Abraham’s fire an ebullition of My soul. Jacob’s grief is but a reflection of My sorrows, and Job’s afflictions a fraction of my calamity.” “Pour out patience upon Me, O My Lord!”—such is His supplication in one of His prayers, “and render Me victorious over the transgressors.” 

- Shoghi Effendi (‘God Passes By’)