It was during the month of December in 1852 that Baha’u’llah was released from the Siyah-Chal  (Black Pit) of Tehran. Here is how Baha’u’llah’s daughter, Bahiyyih Khanum, the Greatest Holy Leaf, recalled the circumstances involved many years later:
We listened eagerly to the accounts she [her mother, Asiyih Khanum] gave to my uncle [Baha’u’llah’s faithful brother, Mirza Musa]. This information came through the kindness of a sister of my grandfather, who was married to Mirza Yusif, a Russian subject, and a friend of the Russian Consul in Tihran. This gentleman, my great uncle by marriage, used to attend the courts to find out some particulars as to the victims chosen for execution day by day, and thus was able to relieve to some extent my mother's overwhelming anxiety as these appalling days passed over us.
It was Mirza Yusif, who was able to help my mother about getting food taken to my father, and who brought us to the two little rooms near the prison, where we stayed in close hiding. He had to be very careful in thus defying the authorities, although the danger in this case was mitigated by the fact of his being under the protection of the Russian Consulate, as a Russian subject.
Nobody at all, of all our friends and relations, dared to come to see my mother during these days of death, but the wife of Mirza Yusif, the aunt of my father.
One day the discovery was made by Mirza Yusif that our untiring enemies, the most fanatical of the mullas, were plotting the death of Mirza Husayn 'Ali Nuri [Baha’u’llah], my father.
Mirza Yusif consulted the Russian Consul; that powerful friend determined that this plan should be at once frustrated.
An amazing scene took place in the Court, where the sentences of death were passed. The Russian Consul rose and fearlessly addressed those in court:
"Hearken to me! I have words of importance to say to you" (his voice rang out, the president and officials were too amazed to reply).
"Have you not taken enough cruel revenge? Have you not already murdered a large enough number of harmless people, because of this accusation, of the absurd falseness of which you are quite aware? Has there not been sufficient of this orgy of brutal torture to satisfy you? How is it possible that you can even pretend to think that this august prisoner planned that silly attempt to shoot the Shah?
"It is not unknown to you that the stupid gun, used by that poor youth, could not have killed a bird. Moreover, the boy was obviously insane. You know very well that this charge is not only untrue, but palpably ridiculous.
"There must be an end to all this.
"I have determined to extend the protection of Russia to this innocent nobleman; therefore beware! For if one hair of his head be hurt from this moment, rivers of blood shall flow in your town as punishment.
"You will do well to heed my warning, my country is behind me in this matter."
An account of this scene was given to my mother by Mirza Musa, when he came for tidings.
Needless to say how eagerly my brother and I listened, and how we all wept for joy.
Very soon afterwards we heard that, fearing to disregard the stern warning of the Russian Consul, the Governor gave orders that my father should be permitted to come forth from that prison with his life. It was also decreed that he and his family were banished.
They were to leave Tihran for Baghdad. Ten days were allowed for preparation, as the beloved prisoner was very ill indeed.
And so he came to our two little rooms.
Oh, the joy of his presence!
Oh, the horror of that dungeon, where he had passed those four terrible months.
(Lady Blomfield, 'The Chosen Highway')
On his release, the Russian Consul is reported to have offered “immediately the protection of his government and every assistance for Baha’u’llah and His family to settle in Russia. Baha’u’llah graciously declined and chose to settle in Baghdad.” (David Hofman, 'Baha’u’llah the Prince of Peace')
 The underground dungeon in Tihran, Iran where Baha’u’llah was chained and incarcerated for four months in 1852 (August through December), together with fellow Babis and 150 criminals. Here, in indescribable conditions, He received the first intimation of His world Mission