Hadith of the Ark ""perished whoever turned away from it"" also comes along." And in his another book, Al-Heithami indicates this hadith as authentic (sahih). According to Dahlan, the authenticity of this hadith is confirmed by different sources. The hadith implies the absolute priority of "Ahl al-Bayt" to all others, otherwise Muhammad would have forbidden to follow them. According to Shia scholars, the only path to salvation is by following the "Ahl al-Bayt", so they must be infallible ("Ma'sum"), otherwise they will mislead their followers. If they are infallible, they must be Imam definitely. According to this hadith, they are the criterion of distinguishing
Introduction to the Science of Hadith clarify that term and not necessarily establish it. He also distinguished his book by responding to the positions of other scholars in a detailed manner. Ibn al-Ṣalāḥ mentioned in his introduction to the "Introduction" 65 chapters, each specific to a particular type or term of hadith terminology before saying that an even larger number was conceivable. He began by discussing "ṣaḥīḥ" (authentic) as the first category, and then "ḥasan" (good) as the second, "ḍa`īf" (weak) the third, "musnad" (supported) the fourth and so on. Ibn Jamāʻah, in his abridgement, divided these terms into four different categories according to subject (and