Caliph al-Amir appointed al-Mamun al-Bata'ihi to the vizarate, who reopened the Dar al-Hikmah in Cairo, which had been closed by al- Afdal in 513/1119, where he immediately learnt many professions supporting the cause of Imam Nizar. Meanwhile, there raised violent reactions in other parts of the Fatimid dominion to this effect, mostly in Syria and Iran. The vizir al-Mamum feared the Nizari Ismaili influence once again penetrating in Egypt, therefore, he arranged for a grand public assembly to publicize the claims of al-Musta'li and refute the rights of Nizar. This meeting was held in 516/1122 at the great hall of the palace and was attended by numerous Fatimid princes and distinguished dignitaries, including Abu Muhammad bin Adam, the head of the Dar al-Hikmah. The Egyptian historians, such as Ibn Muyassar (1231-1278) in 'Tarikh-i Misr' (ed. Henri Masse, Cairo, 1919, pp. 66-67) and Makrizi in 'Itti'az' (Cairo, 1948, 3rd vol., pp. 87-88) have provided a detailed account of the proceedings. In the course of the assembly, various episodes were referred to justify the claims of al-Musta'li. Most significantly, Nizar's full sister, sitting behind a screen in an adjoining chamber, testified that al- Mustansir, on his death-bed, had designated al-Musta'li as his successor, divulging the change of nass to his own sister (Nizar's aunt). At the conclusion, vizir al-Mamun ordered Ibn al-Sayrafi (d. 542/1147), a secretary at the Fatimid chancery, to compile an epistle (sijill) in favour of al-Musta'li, to be read publicly from the pulpits of the mosques in Egypt. This epistle is known as 'al-Hidayat al-Amiriyya' (the advices of al-Amir), or 'ar-Risalatu'l-Amiriyya' (the epistle of al-Amir), which had been written about 28 years after the Nizari-Musta'lian schism. Its copies were also circulated in Syria, where it caused an uproar amongst the Nizari Ismailis in Damascus. The matter was referred to the Nizari Ismaili chief, who immediately wrote a refutation of it. This refutation was read at a meeting of the Musta'lians in Damascus, whose dais forwarded its copies to al-Amir in Cairo, asking him for further guidance. Soon afterwards, al-Amir sent a reply in 517/1123 to his Syrian dais through an epistle under the bombastic title of 'Iqa Sawa'iqa al-irgham'(the fall of the lightning of humiliation), which is treated as an appendix to 'al-Hidayat al-Amiriyya'. The original epistle reached in Syria on Thursday, the 27th Zilhaja, 517 A.H.
'Al-Hidayat al-Amiriyya', or in full, 'al-Hidayat al-Amiriyya li-Mawlana al-Amir fi ithbat Imamat Mawlana al-Musta'li wa'r-radd ala'n Nizariyya', is attributed to the authorship of al-Amir quite incorrectly. It was compiled by al-Sayrafi, and the text was read over and approved by al-Amir. It is almost a bombastic, full of stylistic tricks and void of historical facts, and alludes here and there.
Asaf A.A. Fyzee (1899-1981) published the Arabic text of 'al-Hidayat al-Amiriyya' from Calcutta in 1938 with its introduction and comments, whose few examples are given below:-
In the course of his argument, the author of 'al-Hidayat al-Amiriyya' has to admit the most important fact that Nizar had been officially proclaimed the heir-apparent of his father, and that the provincial agents of the state were duly informed about it (cf. p. 21, 1.12). He further states that the appointment was first cancelled by the subsequent nomination of Nizar's younger brother, Abdullah, and later on by the nass to Musta'li in the last hour of al-Mustansir's life (cf. p. 18, 1.7). Fyzee comments that, 'This nomination at the moment of expiring made under very suspicious circumstances, as we have seen, does not seem very convincing.' (p. 5)
The author further emphasizes the alleged fact that Nizar and Abdullah were both given the title of wali ahdi'l-muslimin, while only Musta'li was called the wali ahdi'l-mu'minin. Fyzee writes in this context that, 'The matter seems to be somewhat dark, although the difference between islam and imam in Muslim theology, and particularly in Ismaili doctrine, is well known. It is difficult to generalize whether this difference in title, even if it was real, implied any material distinction.' (p. 5)
The most amazing thing in all this is the fact that the author quite earnestly admits, and even emphatically defends, the principle of revocation of the nass. Fyzee writes, 'As is known, Ismailism itself came into existence as an independent sect of Islam in circumstance closely resembling the case of Nizar, and the immediate cause of the split of the Shiite community was exactly the defence of the dogma of the irrevocability of the nass. The sect was formed by the followers of Ismail, the son of Imam Jafar as-Sadiq who refused to recognize the legality of the second nass, to Musa al-Kazim.' (p. 6) He further adds, 'It is difficult to believe that in its case the later will could cancel the preceding one, as the author tries to prove. Especially strange would it be to claim that it should be cancelled by the alleged nass fi daqiqati'l-intiqal, i.e. the nomination (made by the Caliph) at the moment of his death, to which the author refers several times, in view of the rather doubtful circumstances which accompanied it.' (pp. 6-7) Fyzee also comments, 'Though the author often refers to this last moment's nass, he never mentions who really was the witness of such an important act. From what is known, it is quite obvious that Nizar and his party were not represented at the moment of the Caliph's death.' (f.n., p. 7)
As Musta'li was only just over 18 years of age, or according to Ismaili historians, 20, at the time of al-Mustansir's death, it is obvious that his wedding could not have been celebrated more than seven years before his father died, i.e. when he was about 13 years of age. It is quite probable that in reality it took place much later. Thus it would appear that during the exceptionally long reign of al-Mustansir, something like 55 years, there was no heir-apparent, until the Caliph, at the memorable wedding, in a rather elusive way, appointed Musta'li, by bestowing upon him the title of wali ahdi'l-mu'minin. Fyzee remarks, 'All this sounds very improbable.' On page 20, 1.2, the author, obviously conscious of this difficulty, goes so far as to say that the nass to Nizar, and later on to Abdullah, was made by al-Mustansir only as a concession to the public impatience, in order to placate his followers. Fyzee writes, 'He apparently does not notice that this implies insincerity of the Imam in his actions.' (p. 7)
With regard to the memorable occasion of the wedding of Musta'li, which plays the key role in the argument of the author, it provides, in addition to the bestowing of the title mentioned above, yet another sign of the elevation of the young prince above his brothers, namely his being seated on the right hand of his father, while all other princes had to sit on the left side. Fyzee writes, 'It is difficult to find in this decisive indication as to whether such arrangement constituted something extraordinary from the point of view of the Fatimid court etiquette. As Musta'li was the centre of the celebration, the hero of the day, perhaps he might have been specially honoured on the occasion, without any prejudice to the rights and dignity of his elder brothers.' (p. 8)
A very interesting story is given by the author (p. 14) in which he mentions the testimony of Nizar's sister. The latter, as the author narrates, in the presence of witnesses publicly denounced the claims of Nizar to the Imamate, and condemned his attitude, invoking curses upon all those who supported him. She said that on several occasiions her father, the last Caliph al-Mustansir, gave her to understand that it was his intention to appoint Musta'li his heir-apparent. She added further that her brother Nizar, on the memorable occasion of Musta'li's wedding to the daughter of al-Afdal, came to her, and said that till then he still cherished the hope of being his father's successor. But after seeing the ostentation with which his father showed his favour towards the youngest prince, by giving him precedence over his elder brothers, he had to give up all hope. Thus, as she said, Nizar was quite conscious that he was acting wrongly when he rose in rebellion. Fyzee writes, 'This story is really interesting in its implications: it is quite possible that a certain estrangement did take place between the father and his elder son, as may happen in any family, of high or low position. This certainly could easily exploited for their own ends by al-Afdal and his party, whom the ascension of Nizar threatened to dislodge from their high position. But at the same time from the words of Nizar quoted by his sister, it appears that until the fateful wedding there was no official act by which Nizar was deprived of his position as heir-apparent.' (p. 9)
The author claims that Nizar and Abdullah swore allegiance to Musta'li on his accession (cf. p. 22, 1.12). Fyzee writes, 'But there are other historians, and they are far from being pro-Nizar, who nevertheless relate that when Nizar was summoned to the palace only to find that his father was dead, and Musta'li was enthroned by the commander-in-chief, he protested, saying that he had a written document concerning his appointment as the heir. He said that he was going to fetch it, left the palace, and then escaped to Alexandria. Thus there is no certainty as to the circumstances of the alleged swearing of allegiance.' (pp. 10-11)
Another decisive argument which the author uses against Nizar is the alleged extinction of his house (cf. p. 23, 1.11), which, according to Ismaili ideas, definitely proves the futility of a person's claims to the Imamate. Fyzee comments, 'As is quite natural to expect, he refuses to believe in the fact that descendants of Nizar continue in Persia.' (P. 11)