What should the Muslim do with regard to scholarly differences of opinion as to whether a hadeeth is sound or weak?
Question

                What should we do if the scholars of hadeeth differ as to whether a hadeeth that has to do with worship is saheeh (sound) or da’eef (weak)?.
Praise be to Allah.
    Firstly: 

    There is no difference among the scholars between scholarly 
    differences of opinion as to whether a hadeeth is saheeh or da’eef, and 
    their differences concerning matters of fiqh. That is because the 
    classification of hadeeth as saheeh or da’eef is subject to ijtihaad and the 
    scholars vary in their knowledge of narrators and isnaads of hadeeth. What 
    one of them knows about the circumstances of a narrator may be unknown to 
    others, and what another finds of corroborating reports may not be available 
    to another. So their rulings on a particular hadeeth may differ for these 
    reasons. Sometimes all of them found the biography of a narrator and the 
    isnaads of a hadeeth, but they varied in the rulings as to whether it was 
    saheeh or da’eef according to their own ijtihaad with regard to evaluating 
    the narrator and according to their view as to whether the hadeeth is free 
    of any problems.  

    Imam al-Tirmidhi said: 

    The imams differed in classing men (narrators) as da’eef 
    (weak), as they differed in other aspects of knowledge.

    Sunan al-Tirmidhi (5/756), 
    Kitaab al-‘Ilal at the end of al-Sunan. 

    Explaining the reasons for differences of opinion among the 
    scholars, Shaykh al-Islam Ibn Taymiyah said: 

    The third reason: Belief that a hadeeth is weak on the basis 
    of ijtihaad, but others disagreed with him, regardless of other isnaads, and 
    regardless of whether he or someone else was correct, or both of them were 
    correct according to those who said that every mujtahid is correct. That is 
    for several reasons, including: the one who narrated the hadeeth thought 
    that one of them was da’eef and the other thought that he was trustworthy. 
    Knowledge of narrators is a vast science, and the one who is correct may be 
    the one who thought it was da’eef, because he had come across a reason to 
    make him think so, or the other one may have been correct because he knew 
    that this reason may not be enough to regard him as da’eef, either because 
    that reason in and of itself is not a problem or because he had an excuse 
    which meant that he could not be classified as da’eef.  

    This is a broad topic for scholars who study narrators and 
    their circumstances, and there may be consensus and differences just as 
    there are among other scholars in their own fields. 

    (Another reason is) that he did not believe that the 
    muhaddith heard the hadeeth from the one from whom he narrated it, but 
    someone else believed that he did hear it for reasons which imply that. 

    (Another reason is) that the muhaddith may have been through 
    two phases, one when he was sound and credible and another when there was 
    confusion about his narrations, such as he got mixed up and his books were 
    burned or lost, so what he narrated when he was sound and credible is saheeh 
    and what he narrated when he was confused is da’eef. So he (the scholar) may 
    not have known which of the two scenarios applied to this hadeeth, but 
    someone else knows that he narrated this particular hadeeth when he was 
    sound and credible. 

    (Another reason is) that the muhaddith forgot that hadeeth 
    and did not remember it afterwards, or he denied having narrated it because 
    he thought that there was a problem which meant that he should leave this 
    hadeeth alone, but another scholar may think that it is something that is 
    valid and may be quoted as evidence. This issue is well known … and there 
    are other reasons too. 

    Majmoo’ al-Fataawa 
    (20/240-242). 

    Secondly: 

    With regard to the Muslim’s attitude towards these 
    differences which occur among scholars with regard to whether a hadeeth is 
    saheeh of da’eef, it is the same attitude as that towards their differences 
    of opinion in fiqh. If he is qualified to distinguish between their 
    opinions, he may decide which of the two rulings concerning one hadeeth he 
    thinks is correct; if he is not qualified to do so, then he should follow 
    the opinion of a scholar (taqleed) and he should accept the verdict of the 
    one who he thinks is more religiously committed and has greater knowledge 
    concerning this matter. He should not be deceived by the fact that he is a 
    faqeeh or scholar of usool or mufassir, rather the one whose verdict of 
    saheeh or da’eef is followed should be prominent in the science of hadeeth, 
    and there is no sin on him if he follows a prominent scholar. If the hadeeth 
    is saheeh according to that scholar and he follows him in that, and it 
    contains a fiqhi ruling, then he must act upon it, but there is no sin on 
    him for not acting upon it if the hadeeth is da’eef. 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 

    If the scholars differed concerning it in their fatwas or 
    what is heard in their exhortations and advice, for example, then he should 
    follow the one who he thinks is closer to the truth in his knowledge and 
    religious commitment. 

    Liqa’ al-Baab il-Maftooh (no. 
    46, question no. 1136) 

    See also the answer to question no.
    22652 for a discussion of the 
    correct attitude towards scholarly differences . 

    And Allaah knows best.