In the whole range of Bahá'u'lláh's Writings, the Kitáb-i-Íqán (The Book of Certitude) has most importance, with the exception of the Kitáb-i-Aqdas (The Most Holy Book). It was revealed in Baghdad about two years before His Declaration, in honour of Háji Mirza Siyyid Muhammad, the Báb's maternal uncle.
The Báb had three maternal uncles. The first to embrace His Faith was Háji Mirza Siyyid Ali, known as Khal-i-A'zam (the Greatest Uncle). It was he who cared for the Báb and, after the passing of His father, was responsible for bringing Him up.
Háji Mirza Siyyid Ali became aware of the spiritual qualities and superhuman powers which his Nephew manifested from an early age. He readily recognized the station of the Báb and became an ardent believer as soon as he became acquainted with His claims. Indeed, next to the Letters of the Living, he was the first person in Shiraz to acknowledge the divine origin of the Message of the Báb. From then on he devoted his life entirely to the promotion of the newly-born Faith and the protection of its youthful Founder. A few months before the martyrdom of the Báb, he was arrested and, upon refusing to recant his faith, was publicly martyred. He is one of the Seven Martyrs of Tihran.
The eldest uncle, Háji Mirza Siyyid Muhammad, although fully aware of the outstanding qualities of his Nephew, was not converted to His Faith until he met Bahá'u'lláh in Baghdad and received the Kitáb-i-Íqán in answer to his questions. The third uncle was Háji Mirza Hasan-'Ali.
For some years Háji Mirza Siyyid Muhammad carried out his business as a merchant away from home, in Bushihr (Bushire), in association with his brother Háji Mirza Siyyid Ali and his Nephew the Báb. When these two left for Shiraz he continued to work on his own and was still in Bushihr when the Báb declared His Mission to His first disciples. Later, when the Báb made His pilgrimage to Mecca, He travelled by way of Bushihr where He stayed at the home of Háji Mirza Siyyid Muhammad. He returned there some months later while journeying back to Shiraz. It was during these visits that Háji Mirza Siyyid Muhammad witnessed a transformation of spirit in the Báb and wrote about it to his own mother and sister (the mother of the Báb) in these words: