Hadith as Sunna, but it is not necessary that a Sunna would have a supporting hadith sanctioning it. Some sources (Khaled Abou El Fadl) limit hadith to verbal reports, with the deeds of Muhammad and reports about his companions being part of the "Sunnah", but not hadith. Joseph Schacht quotes a Hadith by Muhammad that is used "to justify reference" in Islamic law to companions of Muhammad as religious authorities — "My companions are like lodestars." According to Schacht, (and other scholars) in the very first generations after the death of Muhammad, use of hadith from "Sahabah" ("companions" of Muhammad) and
Introduction to the Science of Hadith category, which comprises 21 types, relates to the names of the narrators. This includes the definition of a "ṣaḥābī" (companion), a "tābi`ī" (follower), the time periods of narrators, names and paidonymics among others. Later scholars included additional types of hadith in their own works, with some almost reaching 100. The "Introduction" became the basis for subsequent books in hadith terminology. A number of subsequent scholars followed Ibn al-Ṣalāḥ in the ordering of his book, including al-Nawawī, Ibn Kathīr, al-ʻIraqi, al-Bulqīnī, Ibn al-Jamā`ah, al-Tabrīzī, al-Ṭībī and al-Zirkashī. In many instances this influence was direct, with numerous scholars authoring books indicating its