In a discussion of the exact date of the revelation of the Kitab-i-Iqan, attention has been drawn to a letter dated 17 January 1861 written in Baghdad by Haji Mirza Siyyid Muhammad to his son Vakilu'dDawlih.[‘The Conversion of the Great-Uncle of the Bab’, by Ahang Rabbani] In this letter, Haji Mirza Siyyid Muhammad describes attaining Baha'u'llah's presence. Assuming the accuracy of the date as written, the date of the revelation of the Kitab-i-Iqan can be determined to be just a few days before the writing of the letter, or mid-January 1861. The letter reads in part:
“If you wonder over our state, praised be God and His grace, on the night of the first of Rajab [12 January 1861] we attained the threshold of the Shrines of the twin Imams at Kazimayn.... God willing, the day after next--that is, on the seventh of the month--we will depart this location...
Thank God that one thing I need to write you is that I attained unto the presence of His Holiness Baha [Baha'u'llah], upon Him be God's peace.... He showered us with utmost affection and kindness and asked that we stay for the night, and we remained in His presence. The evident truth is that to be deprived of the blessing of His presence is a mighty and evident loss. May God bestow His grace upon me so that I would everlastingly attain unto the blessing of His presence.[‘The Conversion of the Great-Uncle of the Bab’, by Ahang Rabbani, pp. 34-35.]
Although it has been concluded from this letter that the Iqan was revealed in early January, the letter clearly indicates that Haji Mirza Siyyid Muhammad had returned to Baghdad not earlier than 12 January. Since, according to one of Baha'u'llah's own tablets, the uncle attained Baha'u'llah's presence at least one day after returning from Kazimayn, and the revelation of the Iqan took place during the second time he visited Baha'u'llah (that is, the next day), we may conclude that the revelation of the Iqan must have begun between 14 and 16 January. Although the evidence of the uncle's letter is very significant, it is not a categorical proof. Further evidence which identifies the date of his trip can clarify the issue more decisively
Baha'u'llah Himself has set down the story of the revelation of the Kitab-i-Iqan. In one of His tablets He recounts that one day Siyyid Javad-i-Karbila'i mentioned the return of the Bab's two uncles from Kazimayn to Baghdad and their intention to depart for Iran. Baha'u'llah asks if Siyyid Javad has proclaimed the Faith to them, to which Siyyid Javad replies in the negative. Baha'u'llah then commands Siyyid Javad to go to them and invite them to Baha'u'llah's home. The next day, Haji Mirza Siyyid Muhammad attains the presence of Baha'u'llah, upon which occasion the ocean of divine utterance billows, and at the end Baha'u'llah tells him that He does not wish him to be deprived of recognizing the Blessed Tree which has grown in his family. Haji Mirza Siyyid Muhammad replies that none of the signs of the Qa'im's appearance, as mentioned for centuries, has been realized, and that he is supposed to come with might, dominion, and miracles. Yet people say that the Qa'im is my nephew; how can I accept that? Baha'u'llah permits him to leave, make a list of his questions, and return the following day to receive the answers. The next day Haji Mirza Siyyid Muhammad returns, poses his questions, and the Kitab-i-Iqan is revealed in answer to those questions.[Baha'u'llah, Tablet to Ibn-i-Asdaq, quoted in Kitab-i-Iqan] (Logos and Civilization by Nader Saiedi, pp. 114-116)