and the mursal reports, once their lines of transmission multiply and are free of deliberate collusion—or when their agreement arises unintentionally—are certainly sound. A transmitted report is either truthful, accurately matching the event, or it is false, the transmitter having either lied on purpose or erred. Whenever a report is safe from intentional lying and from error, it is unquestionably true.
So when a ḥadith arrives through two or more independent routes (I say: as in the present ḥadith), and it is known that the informants did not conspire with one another, and that such agreement could not have occurred by chance, it is deemed authentic. The situation resembles a person who relates an incident, detailing the words and actions that took place, then another person—known not to have conferred with the first—relates the same details. One is then certain that the incident is true in its overall substance, for had both of them fabricated it, whether deliberately or by mistake, it would not normally occur that each of them reproduced such particulars—particulars that custom precludes two independent people from matching without prior arrangement. He said: By this method, most reports whose individual chains are weak in this manner become known to be reliable, even though a single chain on its own is insufficient, whether because it is mursal or because its transmitter is weak. He also said:
This foundational rule must be understood, for it is beneficial in reaching certainty about many transmitted matters in ḥadith, Qur’ānic commentary, the accounts of the Prophet’s campaigns, and whatever is reported of people’s words and deeds, and so forth. ⦗97⦘
Hence, when a ḥadith attributed to the Prophet ﷺ is transmitted through two routes while it is known that neither narrator took it from the other, one is sure of its authenticity—especially when it is also known that the transmitters are not people who deliberately lie, the only possible defect being forgetfulness or error on the part of one of them.
Al-Ḥāfiẓ al-ʿAlāʾī cited words to this effect from him in Jāmiʿ al-Taḥṣīl (p. 38), adding: “When the two chains are combined, the report rises to the rank of ḥasan (fair), for the fear arising from the narrators’ weak memories is removed and each chain supports the other.”
Ibn al-Ṣalāḥ said the same in his Muqaddimah, and Ibn Kathīr repeated it in his abridgment. Ibn Taymiyyah—may Allah have mercy on him—then said (p. 352):
“In such cases the narration of an unknown transmitter, one of poor memory, or a mursal report (1) and the like becomes useful. For this reason the scholars would record such ḥadiths and say, ‘It is suitable for corroboration and comparison, though not for other purposes.’”
He then quoted Abū Aḥmad’s statement, “I may write down a man’s ḥadith only for the sake of comparison,” and illustrated this with the example of Ibn Lahīʿah, as mentioned earlier (p. 96).