Muslims is taken as a model of how Muslims should live in this world in order to lead a happy eternal life in the hereafter. This is most obvious in that this sunna, particularly that of the Prophet, became after the Qur_an the second fundamental source of the shari_a, the Law of God. According to Muslim scholars this status of the sunna is advocated both in the Qur_an and in hadiths of the Prophet and was already acknowledged by his Companions. In contrast, Western scholars usually think that the sunna acquired its status as second source of the Law only gradually during the eighth century and that in Sunnite law the hadiths of the Prophet gained the absolute superiority over other expressions of the sunna only in the first half of the ninth century. In Imami Shi_ite law the traditions of the Prophet did not acquire such a superiority but are considered equal in value with that of the imams.
The important role that the hadiths came to play in Muslim scholarship in general, and for the establishment of the shari_a in particular, induced Muslim scholars to scrutinize the tradition material critically and to define rules as to which hadiths could be accepted and which must be rejected. The traditional Muslim hadith criticism focused on the chains of transmitters (isnads), which accompany a hadith, but also checked whether its content (matn) is compatible with other recognized traditions and with the Qur_an.

سنّتهاي پيامبر و صحابيان او، در بردارنده الگويي براي زندگي مسلمانان در جهت دستيابي به رستگاري در جهان آخرت ميباشد. واضح است که اين سنّتها، به‌خصوص احوال و اقوال و تقرير پيامبر، بعد از قرآن، به عنوان دومين منبع مهم شريعت، شناخته شود. بر اساس گفتههاي محققان اسلامي، اين تعريف از سنّت، به وسيله قرآن و احاديثي از پيامبر، که صحابه آن را بازگو کردهاند تاييد شده است. در عوض، نگاه مستشرقان اين است که سنّت، جايگاهش را به عنوان دومين منبع شريعت، نهايتاً در طول قرن هشم پيدا کرده است، ولي در فقه اهل سنّت، گفتار پيامبر فقط در نيمه اول قرن9 نسبت به ساير بيانات مربوط به سنّت، برتري يافته است، و در فقه شيعه، احاديث پيامبر برتري خاصي ندارند، بلکه از نظر ارزش، با احاديث ساير ائمه، برابر است.
نقش مهمي که حديث در تحقيقات مسلمين، به طور عام، و فقه پژوهي، به طور خاص، بازي ميکند، محققان مسلمان را تشويق کرده که موضوعات حديثي را به روش انتقادي بررسي کنند، و قوانيني در مورد احاديث و تعيين اين‌که کدام قابل قبول وکدام مردود است، وضع کنند و نقد سنّتي حديث، به زنجيره راويان همراه متن، توجه ويژه دارد. همچنين اين نکته را نيز مد نظر دارد که آيا حديث با احاديث مشهور و با قرآن، موافقت دارد يا خير.

This led among the Sunnites to a classification of hadiths in four lasses:(1) sahih (sound); (2) hasan (fair); (3) da_if (weak), with some subcategories of this class; and (4) mawdu_ (spurious Additionally, special classification systems were developed for the evaluation of isnads and matns. The critical evaluation of the hadiths found its expression in special compilations in which their authors collected the hadiths, that they considered reliable or accepted. The “six books” (see the section “Collections” below), which among the Sunnites acquired an almost canonical status, belong to this type of collection. Nevertheless, the evaluation of particular hadiths, even of those contained in the most revered collections, remained disputed in Muslim scholarship.
In Imami Shi_ism hadith criticism was less sophisticated and appeared late because the isnads consisted in large part of the (infallible) imams. In modern times the Muslim debate about the reliability of the hadiths got a new impetus. Reform-minded scholars and intellectuals tried to revise the issue of which hadiths are essential and binding for a Muslim and which are not.