The story of this Declaration is told by H. M. Balyuzi in his short biography Baha'u'llah . The following is an extract:
"Baha'u'llah moved to the garden of Ridvan, outside the gates of Baghdad. The Babis thronged there to see the last of their Beloved so cruelly torn from their midst. It was the twenty-first day of April. With tears in their eyes they gathered around Him. He was calm, serene, and unruffled. The hour had struck. To that company Baha'u'llah revealed Himself - He was the Promised One in Whose path the Bab had sacrificed his life, "Him Whom God will make Manifest,' the Shah Bahram, the Fifth Buddha, the lord of Hosts, the Return of Christ, the Master of the Day of Judgment. A deep silence fell upon the audience. Heads were bent as the immensity of that Declaration touched the consciousness of men. Not a breath of dissent - one and all they threw themselves at His feet. Sadness had vanished; joy, celestial joy, prevailed."
1971 - 'Abdu'l-Bahá The Centre of the Covenant of Bahá'u'lláh (H M Balyuzi)
Enemies were active again. Because the fame of Baha'u'llah was spreading far and wide, they gathered their forces for a further onslaught. Their voices became strident, and Nasiri'd-Din Shah was alarmed. Responding to the pleadings of the Iranian Ambassador, the Ottoman Government decided to call Baha'u'llah to Constantinople.
Prior to His departure, Baha'u'llah moved to the garden of Najib Pasha on the outskirts of Baghdad. Later the Baha'is came to know it as the Garden of Ridvan. There Baha'u'llah revealed His Station and His Mission. The Day of Days had come - 'the Day whereon naught can be seen except the splendours of the Light that shineth from the face of Thy Lord, the Gracious, the Most Bountiful.'
In a letter which 'Abdu'l-Baha wrote during the twelve days' sojourn in the Garden of Ridvan, He traced the course-three years long - of plots, negotiations, and pressures that had been brought to bear on the Ottoman Government. A request to deliver Baha'u'llah and His dependents to the Persian officials was firmly rejected. Other governments were next asked to use their powers of persuasion. In the end the Sublime Porte [Bab-i-'Ali - the seat of power in Constantinople] agreed to move Baha'u'llah away from the vicinity of Persia. 'Abdu'l-Baha further related:
The third day after Ramadan(15) when, in observance of the festival, my uncle and I called on the Pasha [Namiq Pasha, the Vali (governor-general) of 'Iraq], he expressed his eagerness to meet Him [Baha'u'llah]. The Pasha, however, wanted the meeting to be at his own house. He [Baha'u'llah] replied that He did not wish to go to the Governorate, but if the Pasha desired to meet Him, the meeting could take place in the mosque. He went to the mosque, as did the Pasha, but on entering it the Pasha turned back and went away. Later he sent his own vizier to Baha'u'llah's presence, with letters from the Sadr-i-A'zam (prime minister), and also this message: 'I came to the mosque, but was ashamed to broach such matters at the first encounter.' The vizier gave an account of all that had transpired. Then he said: 'What the Pasha asked to know was this - whether you preferred not to leave. Should it be so, if you will write and inform the Sadr-i-A'zam, we shall forward your letter to him. But if you should desire to leave, that would be your own choice.' He [Baha'u'llah] replied: 'If the Government displays proper respect, I will choose, for certain reasons, to reside awhile in those regions.' Then the Pasha sent Him this message: 'I shall carry out your wishes and do what you say.'
The Governor-General, 'Abdu'l-Baha further wrote, had called in person at the garden of Najib Pasha, to pay his respects to Baha'u'llah and to show his esteem and affection. And the discomfiture of the foe is apparent in these, the concluding lines of that historic letter:
Such hath been the interposition of God that the joy evinced by them hath been turned to chagrin and sorrow, so much so that the Persian Consul-General in Baghdad regrets exceedingly the plans and plots which the schemers had devised. Namiq Pasha himself on the day he called on Him [Baha'u'llah] stated: 'Formerly they insisted upon your departure. Now, however, they are even more insistent that you should remain.' They plotted and God plotted, and God is the best of plotters [Qur'an 3:47].
Departure and Journey
On May 3rd 1863, the exiles set out on their long journey to the capital of the Ottoman Empire. Unlike the lonely exodus of two years before, this time they were accompanied by a number of devoted people for whom the reality of heaven was the presence of Baha'u'llah. It was a triumphal march. Everywhere Baha'u'llah was received with reverence by the officers of the state. 'Abdu'l-Baha was then a youth of nineteen, handsome, gracious, agile, zealous to serve, firm with the wilful, generous to all. He strove hard to make the toil of a long journey less arduous for others. At night He was among the first to reach the halting-place, to see to the comfort of the travellers. Wherever provisions were scarce, He spent the night in search of food. And at dawn He rose early to set the caravan on another day's march. Then the whole day long He rode by the side of His Father, in constant attendance upon Him. It took them one hundred and ten days to reach the port of Samsunon the Black Sea, where they embarked for Constantinople, and arrived at the metropolis of the Ottoman Empire on August 16th 1863.
197? - Adib Taherzadeh's Summary
During the twelve days that Bahá'u'lláh remained in the Garden of Ridvan, great numbers came to pay their respects to Him. Among them were notables and dignitaries of the city of Baghdad, men of learning and culture, as well as the mass of the people who were His admirers. As to the believers, Bahá'u'lláh would summon a number of His companions to come to Him each day and would dismiss them in the evening. Only those without family ties were allowed to remain for the night, when some of them would keep vigil around His tent.
Of the twelve days that Bahá'u'lláh stayed in the Garden of Ridvan, three are regarded as Holy Days: the first day on which He declared Himself, the ninth day when all His family joined Him and rejoiced at His Declaration, and the twelfth day when He left that garden.