Noah in rabbinic literature "Sefer haYashar" describes another method for distinguishing them: the clean animals and fowls crouched before Noah, while the unclean ones remained standing. A difference of opinion concerning Noah prevails also with regard to his entering into the ark. According to some rabbis, Noah's faith was so small that he did not enter the ark until he stood ankle deep in water (Genesis Rabba xxxii. 9); others declare, on the contrary, that Noah waited for God's directions to enter the ark, just as he awaited His permission to leave it (ib. 34.4; Midrash Agadat Bereshit, in Jellinek, "B. H." iv. 11).
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