God has preserved both the Quran and the Prophetic traditions. The Quran is preserved to the extent that countless Muslims across the world have memorised the same words in exactly the same order and manner. In terms of Prophetic traditions, they have been preserved by generations of scholars who have dedicated their lives to the pursuit of classifying traditions and sorting them.
There are complete sciences which are focused on the preservation of Prophetic traditions. These sciences cover everything from the study of narrators to the explanation of difficult terms in some traditions. Through this detailed and methodical study, scholars have been able to sift authentic and strong traditions from weak and unreliable narrations. They have earmarked narrators who are unreliable due to character flaws or memory defects, and have meticulously followed each narrator, when and where they lived, and who they did and did not meet so as to verify that there are no breaks or missing links between narrators.
Authentic narrations are called ‘sahih’ or authentic. This means that these traditions have been relayed by a continuous and unbroken chain of trustworthy and reliable narrators, and that there are no irregularities or defects in the tradition. If one of the above conditions is not met, such as the chain is broken, a narrator is unreliable or known to have been forgetful or some other irregularity is found, the tradition is labelled as ‘da’if’ or ‘weak’.
In this way, we know what to follow and not follow, and therefore ensure that our practice of Islam remains as authentic and pure as possible to the practice of the Messenger Muhammad.