To whom is the book Nahj al-Balaaghah attributed?
Question

                I would like to ask how authentic the book Nahj al-Balaagha is and what your opinion of it is?
Praise be to Allah.
    The book Nahj al-Balaaghah is one of the books that 
    are attributed to Ameer al-Mu’mineen ‘Ali ibn Abi Taalib (may Allah be 
    pleased with him), but it contains many things concerning which those who 
    claim to be Muslims have disputed. Following the great scientific principle 
    which was followed by the imams of Islam in obedience to the shar’i command 
    to verify reports, we have no choice but to refer to the scholars and 
    specialists to check on the veracity of the things that are attributed to 
    ‘Ali (may Allaah be pleased with him), because what is narrated from the 
    Sahaabah (may Allaah be pleased with them) has an effect on sharee’ah, 
    especially in the case of someone like Ameer al-Mu’mineen ‘Ali (may Allaah 
    be pleased with him), concerning whom some people have exaggerated or fallen 
    short, but Allaah guided the Ahl al-Sunnah to follow a middle course. 

    By referring to the words of the scholars concerning this 
    book and comparing its contents with what has been proven with saheeh 
    isnaads from ‘Ali (may Allaah be pleased with him), it becomes clear that 
    there is material in this book that contradicts what was proven from him 
    (may Allaah be pleased with him). So we should look at what some of these 
    great scholars have said: 

    Imaam al-Dhahabi (may Allaah be pleased with him) said in his 
    biography of al-Murtada ‘Ali ibn Husayn ibn Moosa al-Moosawi (d. 436 AH): I 
    said, he was the compiler of the book Nahj al-Balaaghah which is attributed 
    to Imam ‘Ali (may Allaah be pleased with him), but the reports contained 
    therein have are no isnaads. Some of it is false and some of it is true, but 
    it contains some frabricated reports of things that the Imam would never 
    have said. But who is the fair-minded man who would look at it in an 
    objective manner?! It was said that it was compiled by his brother Shareef 
    al-Radiy. It includes slander against the companions of the Messenger of 
    Allaah  (peace and blessings of Allaah be upon him); we seek refuge with 
    Allaah from knowledge that is of no benefit.

    Siyar A’laam al-Nubala’, 17/589 

    Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) 
    said: “Most of the khutab (sermons) that the author of Nahj al-Balaaghah 
    includes in his book are lies against ‘Ali. ‘Ali (may Allaah be pleased with 
    him) is too noble and too worthy to have uttered such words. But these 
    people fabricated lies and thought that they were praise, but they are 
    neither truth nor praise. Whoever says that the words of ‘Ali or any other 
    human being are above the words of any other created being is mistaken, for 
    the words of the Prophet  (peace and blessings of Allaah be upon him) 
    are above his words, and both of them are created beings. Moreover the 
    correct meanings that are to be found in the words of ‘Ali are to be found 
    in the words of others, but the author of Nahj al-Balaaghah and his 
    ilk took many of the things that people say and made them the words of ‘Ali. 
    There are some words narrated from ‘Ali that he did say, and some of them 
    are true words that would have been befitting for him to say, but in fact 
    they are the words of others. Hence in Kalaam al-Bayaan wa’l-Tabyeen 
    by al-Haafiz and in other books there are words narrated from people other 
    than ‘Ali and the author of Nahj al-Balaaghah attributed them to 
    ‘Ali. If these sermons which were transmitted in Nahj al-Balaaghah 
    were really spoken by ‘Ali, they would have been found in other books that 
    existed before this book was written, and they would have been narrated from 
    ‘Ali with isnaads and otherwise. It is known from those who are well versed 
    in the study of narrations that many of them (these sermons) – indeed most 
    of them – were unknown before this, therefore it may be concluded that they 
    are fabrications. So the narrator should state in which book they are 
    mentioned, who narrated it from ‘Ali, and what its isnaad is. Otherwise, 
    anybody could say something and claim that it was said by ‘Ali. Those who 
    are well-versed in the knowledge of the hadeeth scholars and of reports and 
    isnaads and are able to tell what is sound and what is not sound would know 
    that these people who transmitted reports from ‘Ali are the least likely 
    people to know about reports and be able to distinguish the sound from the 
    unsound.

    Manhaaj al-Sunnah al-Nabawiyyah, 
    8/55. 

    Other scholars who pointed out the lies in this book was 
    al-Khateeb al-Baghdaadi, in al-Jaami’ li Akhlaaq al-Raawi wa Adaab 
    al-Saami’, 2.161; al-Qaadi Ibn Khalkaan; al-Safadi, and others. The 
    things that have been said against it may be summarized in the following 
    points: 

    1.There are seven generations of 
    narrators between ‘Ali (may Allaah be pleased with him) and the author of 
    this book, and he did not mention any name whatsoever. Hence we cannot 
    accept his words without an isnaad. 

    2.If these narrators are 
    mentioned, it is essential to research about them and find out whether they 
    are trustworthy.

    3.The fact that most of these 
    sermons did not exist before this book was written indicates that they were 
    fabricated.

    4.Al-Murtada – the author of the 
    book – was not one of the scholars of reports, rather he was one of those 
    whose religious commitment and competence were debatable.

    5.The slander that it contains 
    against the leading Sahaabah is sufficient to count it as false.

    6.The insults and slander that it 
    contains are not the characteristics of the believers, let alone their 
    leaders such as ‘Ali (may Allaah be pleased with him).

    7.It contains contradictions and 
    clumsy expressions from which it may be known for certain that it was not 
    produced by one who was prominent in eloquence and fluency.

    8.The fact that the Raafidah 
    accept it and are certain that it is as true as the Qur’aan, despite all 
    these objections, indicates that they do not pay attention to verifying 
    sources and ensuring that they are sound with regard to the matters of their 
    religion.

     Based on the above, it is clear that this book cannot be 
    attributed to ‘Ali (may Allaah be pleased with him), therefore nothing in it 
    can be used as evidence in matters of sharee’ah, no matter what the issue 
    is. But whoever reads it in order to find out what it contains of eloquence, 
    the ruling is the same as that on all other books on Arabic language, 
    without attributing its contents to Ameer al-Mu’mineen ‘Ali (may Allaah be 
    pleased with him).

     See Kutub hadhdhara minha al-‘Ulama’, 2/250