The “first” events that took place in Baghdad while Bahá’u’lláh was there

And finally, before the gaze of the diversified communities that dwelt within its gates,

• the first phase in the gradual unfoldment of a newborn Revelation was ushered in,
• the first effusions from the inspired pen of its Author were recorded,
• the first principles of His slowly crystallizing doctrine were formulated,
• the first implications of His august station were apprehended,
• the first attacks aiming at the disruption of His Faith from within were launched,
• the first victories over its internal enemies were registered, and
• the first pilgrimages to the Door of His Presence were undertaken.

- Shoghi Effendi  (‘God Passes By’, chapter 7)

The resulting increase of Baha’u’llah’s admirers

Around the heavenly Table, spread in its very heart, clergy and laity, Sunnís and Shí‘ahs, Kurds, Arabs, and Persians, princes and nobles, peasants and dervishes, gathered in increasing numbers from far and near, all partaking, according to their needs and capacities, of a measure of that Divine sustenance which was to enable them, in the course of time, to noise abroad the fame of that bountiful Giver, swell the ranks of His admirers, scatter far and wide His writings, enlarge the limits of His congregation, and lay a firm foundation for the future erection of the institutions of His Faith. 

- Shoghi Effendi  (‘God Passes By’, chapter 7)

References to the the House of Bahá’u’lláh in Baghdad and its designation as “a center of pilgrimage”

The House of Baha'u'llah in Baghdad after
restoration in early 1930's

Within its walls

• the “Most Great House of God,”
• His “Footstool” and the “Throne of His Glory,”
• “the Cynosure of an adoring world,”
• the “Lamp of Salvation between earth and heaven,”
• the “Sign of His remembrance to all who are in heaven and on earth,”
• enshrining the “Jewel whose glory hath irradiated all creation,”
• the “Standard” of His Kingdom,
• the “Shrine round which will circle the concourse of the faithful” was irrevocably founded and permanently consecrated.
• Upon it, by virtue of its sanctity as
• Bahá’u’lláh’s “Most Holy Habitation” and
• “Seat of His transcendent glory,”
• was conferred the honor of being regarded as a center of pilgrimage second to none except the city of ‘Akká, His “Most Great Prison,” in whose immediate vicinity His holy Sepulcher, the Qiblih of the Bahá’í world, is enshrined.

 - Shoghi Effendi  (‘God Passes By’, chapter 7)

The spiritual impact of Bahá’u’lláh’s presence on Baghdad

From it radiated, wave after wave, a power, a radiance and a glory which insensibly reanimated a languishing Faith, sorely-stricken, sinking into obscurity, threatened with oblivion. From it were diffused, day and night, and with ever-increasing energy, the first emanations of a Revelation which, in its scope, its copiousness, its driving force and the volume and variety of its literature, was destined to excel that of the Báb Himself. Above its horizon burst forth the rays of the Sun of Truth, Whose rising glory had for ten long years been overshadowed by the inky clouds of a consuming hatred, an ineradicable jealousy, an unrelenting malice. In it the Tabernacle of the promised “Lord of Hosts” was first erected, and the foundations of the long-awaited Kingdom of the “Father” unassailably established. Out of it went forth the earliest tidings of the Message of Salvation which, as prophesied by Daniel, was to mark, after the lapse of “a thousand two hundred and ninety days” (1280 A.H.), the end of “the abomination that maketh desolate.” 

- Shoghi Effendi  (‘God Passes By’, chapter 7)

Some references to the city of Baghdad

In that city, described in Islamic traditions as “Ẓahru’l-Kúfih,” designated for centuries as the “Abode of Peace,” and immortalized by Bahá’u’lláh as the “City of God,” He, except for His two year retirement to the mountains of Kurdistán and His occasional visits to Najaf, Karbilá and Káẓimayn, continued to reside until His banishment to Constantinople. To that city the Qur’án had alluded as the “Abode of Peace” to which God Himself “calleth.” To it, in that same Book, further allusion had been made in the verse “For them is a Dwelling of Peace with their Lord … on the Day whereon God shall gather them all together.” 

- Shoghi Effendi  (‘God Passes By’, chapter 7)

About a month after Bahá’u’lláh’s family arrived in Baghdad they rented a house in “ an old quarter of the city”

Soon after His arrival the representative of the Sháh’s government, stationed in Baghdád, called on Him, and suggested that it would be advisable for Him, in view of the many visitors crowding that center of pilgrimage, to establish His residence in Old Baghdád, a suggestion with which He readily concurred. A month later, towards the end of Rajab, He rented the house of Hájí ‘Alí Madad, in an old quarter of the city, into which He moved with His family. 

- Shoghi Effendi  (‘God Passes By’, chapter 7)

Baha’u’llah then proceeded to Kázimayn about three miles north of Baghdád

From there He proceeded, a few days after, to Kázimayn, about three miles north of the city, a town inhabited chiefly by Persians, and where the two Kázims, the seventh and the ninth Imáms, are buried. 

- Shoghi Effendi  (‘God Passes By’, chapter 7)