Do the rules of Hadith science, such as the use of isnad, distinguishing between authentic (sahih) and weak (da'if), and al-Jarh wa al-Ta'dil (discrediting and accrediting of narrators), have a basis in the Quran and Sunnah, or are they scholarly efforts by the Muhaddithun (Hadith scholars) to preserve the Sunnah?

The science of the fundamentals of Hadith (Usul al-Hadith) is built upon rational rules, methodological principles, and empirical foundations that the Hadith scholars (Muhaddithun) arrived at through their accumulated experience in transmitting narrations and verifying their authenticity. However, these rules, in their general philosophy, are legal (Shariah) principles derived from the Quran and Sunnah. Among these fundamental legal principles are: the severe prohibition of lying in Hadith, the non-acceptance of a corrupt person's (fasiq) narration, the condition of the narrator's uprightness (adalah), constant verification and investigation, caution against rejected narrations (munkarat al-akhbar), avoiding the narration of falsehoods, considering precision and memory as criteria for trustworthiness, caution against being accused due to numerous strange narrations (ghara'ib), seeking evidence and proof, and searching for knowledge and certainty away from conjecture and illusion. As for the precise details of the fundamentals of Hadith, they are the product of intellectual effort that translates those general principles into practical methodological laws.