Hadith same text are each counted as individual ahadith. If, say, ten companions record a text reporting a single incident in the life of Muhammad, hadith scholars can count this as ten hadiths. So Musnad Ahmad, for example, has over 30,000 hadiths—but this count includes texts that are repeated in order to record slight variations within the text or within the chains of narrations. Identifying the narrators of the various texts, comparing their narrations of the same texts to identify both the soundest reporting of a text and the reporters who are most sound in their reporting occupied experts of hadith
Hadith of the Ark follows: Behold! The similitude of my Ahlul Bayt, is like that of the Ark of Noah: The one who embarks it, will have saved himself, and the one who turns away from it, is doomed. Many Sunni books narrate this Hadith. Some significant Sunni books that narrate this Hadith are: Al-Hakim al-Nisaburi, one of the greatest Sunni scholars, narrated this hadith as authentic (sahih) in his Mustadrak. Al-Heithami in his book ("written against Shia") states: By many narrations of this hadith which strengthen each other;""certainly Ahl al-Bayt are like the Ark of Noah, saved Whoever boarded"", and in Sahih Muslim