However, what is often forgotten by many Muslims is that the above divine promise also includes, by necessity, the Sunnah of the Prophet Muhammad, sallallaahu alayhi wa sallam, for it is the practical example of the implementation of the Quranic guidance, the Wisdom taught to the Prophet, sallallaahu alayhi wa sallam, along with the Scripture, and neither the Quran nor the Sunnah can be understood correctly without recourse to the other.
Allaah preserved the Sunnah by enabling the Companions, may Allaah be pleased with them, and their followers, may Allaah have mercy on them, to memorize, write down and pass on the statements of the Messenger of Allaah, sallallaahu alayhi wa sallam, and the descriptions of his way, as well as to continue the blessings of practicing the Sunnah. Later, as the purity of the knowledge of the Sunnah became threatened, Allaah caused the Muslim nation to produce outstanding individuals of incredible memory-skills and analytical expertise, who journeyed tirelessly to collect hundreds of thousands of narrations and distinguish the true words of precious wisdom of their Messenger, sallallaahu alayhi wa sallam, from those corrupted by weak memories, from forgeries by unscrupulous liars, and from the statements of the enormous number of scholars, the Companions and those who followed their way, who had taught in various centers of learning and helped to transmit the legacy of Muhammad, sallallaahu alayhi wa sallam – all of this achieved through precise attention to the words narrated and detailed familiarity with the biographies of the thousands of reporters of Hadeeth. Action being the best way to preserve teachings, the scholars of Islam also revived the practice of the blessed authentic Sunnah.
Among the sciences of Hadeeth is the study of the chain of reporters (the Isnaad). Many Muslim scholars have specialized in this field. It includes identifying the name of each and every narrator (reporter), his character (his truthfulness, piety, public behavior), his ability and reputation as a memorizer and the types of narrations he is known to report, whether authentic, weak, fabricated, etc. In addition, each narrator should be identified by a rating given by other narrators who knew him. So all of these and many other details must be considered to know the degree to which a Hadeeth may be used as a basis for Islamic belief or practice (Sharee’ah), or merely as a point of interest (not to be attributed to the sayings, etc. of the Prophet, sallallaahu alayhi wa sallam).
After the Book of Allaah (The Quran), the books of Hadeeth collection that were collected by Imaams Bukhaari and Muslim, may Allaah have mercy upon them, are considered by the Muslim scholars to be the most authentic books of Hadeeth. However, there are other famous scholars in the field who compiled books of Hadeeth such as; Abu Daawood (d.275), At-Tirmithi (d. 279), An-Nasaa’i (d. 303) and others may Allaah have mercy upon them.