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-Kattānī. `Āʼishah bint `Abd al-Raḥmān said in the foreword of her edition of the "Introduction": His book about the sciences of hadith is the best known of his works without comparison, to the extent that it is sufficient to say, "the Book of Ibn al-Ṣalāḥ", the intent being understood due to its popularity and stature. With the previous scholars, its subject matter overcame it, thus being referred to as, "the Book of Ibn al-Ṣalāḥ about `Ulūm al-Ḥadīth" or as he referred to it in its opening pages, "the Book of Familiarity with the Types of `Ulūm al-Ḥadīth". It has become