and it is the position stated by Abū Ya‘lā, Abū al-Khattāb, Abū al-Hasan ibn al-Zāghūnī, and other Hanbalī scholars like them. It is also the position stated by Shams al-Dīn al-Sarakhsī and other Hanafī scholars like him. If consensus affirming the truth of a report establishes its certainty, then what counts here is the consensus of scholars knowledgeable in hadith, just as, in consensus concerning rulings, what counts is the consensus of scholars knowledgeable in commands, prohibitions, and permissions.

“The point here” is that multiple routes of transmission, where mutual awareness or agreement is ordinarily ruled out, yield certain knowledge of the substance of what is transmitted. This is particularly useful in studying the circumstances of transmitters. In such cases, benefit can be derived from reports transmitted by someone whose reliability is unknown, someone with a poor memory, or through a disconnected chain, and the like.

For this reason, scholars would record such hadiths and say, “What is unsuitable for other purposes may be suitable for corroboration and comparison.” Ahmad said, “I may record a man’s hadith in order to compare it with other reports.” He cited as an example ‘Abd Allāh ibn Lahī‘a, the judge of Egypt. He was among the most prolific transmitters of hadith and among the best of people. However, because his books were burned, errors entered his later narrations. His reports thus came to be used for comparison and corroboration. His narrations are frequently paired with those of al-Layth ibn Sa‘d, who was an authoritative, thoroughly reliable leading scholar.

Just as scholars use the hadiths of someone with a poor memory for corroboration and comparison, they also judge certain reports of a trustworthy, truthful transmitter with accurate retention to be weak when evidence shows them that he made mistakes in those reports. They call this “the study of hidden defects in hadith.”