Hadith of the Quran and Sunnah accept the authenticity of the related Hadith of the two weighty things ("Hadith al-Thaqalayn"). In this hadith, Muhammad referred to the Qur'an and "Ahl al-Bayt" ('people of the house', Muhammed's family) as the two weighty things. Although the hadith is accepted by both Sunnis and Shi'as, the two groups differ on the exact wording of what Muhammad said, as well as how to interpret these words. The Shi'as use the Hadith of the two weighty things to prove their claim that Muhammad meant for all his successors to be from his own family ("Ahl al-Bayt"). The Sunnis reject this view
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