Hadith root of why there is no single "fiqh" system, but rather a collection of parallel systems within Islam. Much of early Islamic history available today is also based on the hadith, although it has been challenged for its lack of basis in primary source material and the internal contradictions of the secondary material available. Hadith may be "hadith qudsi" (sacred hadith) — which some Muslims regard as the words of God (Arabic: Allah) — or "hadith sharif" (noble hadith), which are Muhammad's own utterances. According to as-Sayyid ash-Sharif al-Jurjani, the hadith qudsi differ from the Quran in that the former
Introduction to the Science of Hadith al-Ṣalāḥ, in his "Introduction", codified the terminology established by those scholars before him based upon his reading of their works. He did so by citing some of those scholarly statements in the earlier works and deducing from them common terms and definitions in the manner of a scholar authoring a book of "fiqh" (jurisprudence). In this manner, his book was based upon those principles established by the earlier hadith specialists combined with some elements of "fiqh". An example of this would be the inclusion of the division of hadith into "mutawātir" and "āḥād". He therefore only mentioned the statements of