This expansive knowledge of the difference of opinion and issues of fiqh and usul al-fiqh placed ibn Mundhir in excellent grasp of the knowledge of the issues upon which the Islamic community agreed, thereby permitting him to author the book al-Ijma’. Anyone who knows of this topic and reads this book with an open mind will come to know that this book is the best of its kind on the this subject. For this reason ibn Qudamah, in al-Mughni, quotes often from al-Ijma’ and from ibn Mundhir’s other works. Also, [Imam] al-Nawawai said in al-Majmu’, “Anything I quote from al-Ijma’ of ibn Mundhir is an example of excellence in this science.” Ibn Hajar and al-Qurtubi also quoted from him as did ibn Rushd in his book Bidayat al-Mujtahid.
The author is Muhammad b. Ibrahim al-Mundhir, Abu Bakr al-Nisaburi. He was a great scholar in the various Islamic sciences and disciplines. He eventually resided in Makkah and became the Shaykh of the Haram (the Holy Sanctuary). He later died there around the year 318 AH. The scholars have said the following about him:
Adh-Dhahabi said, “The unique scholar of hadith and jurisprudence, and the Shaykh of the Haram, the one who authored books, the likes of which have never been written.”
An-Nawawi said, “The famous imam and one of the imams of Islam. Everyone has agreed to the fact that he was an imaam, virtuous, and very knowledgeable both in the field of hadith and fiqh…He is at the highest level of knowledge when it comes to which hadiths are authentic and which ones are weak.”
As-Subki said, “The imaam, Abu Bakr an-Nisaaboori, the one who resided in Makkah and one of the great scholars of this Nation. He was an imaam, a mujtahid, a haafidh, and extremely pious.”
Ibn Hajar said, “The hafidh, the great scholar, the author of many works. He was upright and truthful from what I know.”
Ibn Khalkaan said, “He was a faqih and an absolute scholar.”