"vast biographical dictionaries" to check against the isnads of individual hadith. Not all transmitters were evaluated for these characteristics and rated. Companions of the prophet (ṣaḥāba) were traditionally considered to possess collective moral turpitude or taʿdīl, by virtue of their exposure to the Prophet, so that they all possessed ʿadāla without needing to be evaluated. (This quality was similar to that of Prophetic infallibility (ʿiṣma) but of course lower in level.) Shaykh Muhammad Zakariya al-Kandahlawi has mentioned that Imam Bukhari (the famous compiler of "sound" hadith) listed the following as criterion for a muhaddith: The four things which one must write are: The hadith of the Prophet and his rulings The sayings of the Sahaba and the status of each sahabi (companions of the prophet) The sayings of the Tabieen (i.e., the Salaf-us Salaheen who met the Sahaba, but did not meet the Blessed Prophet). The level of each of the Tabieen. Who amongst them was reliable and who was unreliable Knowledge of all the narrators who narrate hadith and their history The history of the narrators must include four things: Their Isma-ul-Rijjal (biographies) Their kunniyaat (nicknames) Their place of settlement Their date of birth and date of death (to verify whether this person met the people whom he narrated from) Traditional importance of the sanad The second criteria after judging the general ability and moral probity of the transmitters, is the "continuity" of the chain of transmission of the hadith. The transmitters must be shown to have received the accounts of the prophet "in an acceptable manner from the preceding authority in the chain". Transmitters must have lived during the same period, they must have had the opportunity to meet, and they must have reached sufficient age at the time of transmission to guarantee their capacity to transmit. Early religious scholars stressed the importance of the sanad. For example, according to an early Quranic exegete, Matr al-Warraq, the verse from the Quran, “Or a remnant of knowledge,” refers to the isnad of a hadith. In addition, Abd Allah ibn al-Mubarak said, “The isnad is from the religion; were it not for the isnad anyone could say anything they wanted.” According to Ibn al-Salah, the sanad originated within the Muslim scholastic community and remains unique to it. Ibn Hazm said that the connected, continuous sanad is particular to the religion of Islam: the sanad was also used by the Jewish