Most of the time a person is overtaken by illness; throughout the days of his sickness his faculty of recall is weakened, and he departs—may Allah envelop him in mercy—while still in that altered state. Shortly before his death his mind becomes confused and the knowledge he once held fades; when his soul is taken, death erases his memorization altogether.
So what of it? Is a scholar to be censured for something as ordinary as this? Never, by Allah—certainly not a titan of memorization and accuracy such as he.
Indeed, to the best of our knowledge, the only narration that the critics regarded as unusual in all of Ibn Rāhwayh’s vast learning is a single report: his transmission from Sufyān ibn ʿUyaynah, from al-Zuhrī, from ʿUbayd Allah ibn ʿAbd Allah, from Ibn ʿAbbās, from Maymūnah, concerning the mouse that fell into clarified butter. Ishāq alone, to the exclusion of all the other students of Sufyān, inserted into the wording the additional phrase, “and if it has melted, then do not go near it.” (1)
Most likely the error crept in through one of the later transmitters, or through the narrator who related it from Ishāq.
(1) Reported by al-Bukhari, 9/576 (Book of Slaughtering and Hunting, chapter: “If a mouse falls into solid or melted clarified butter”); by al-Tirmidhi, no. 1799 (Book of Foods, chapter: “The mouse that dies in butter”); by Abu Dawud, no. 3841 (Book of Foods, chapter: “A mouse that falls into butter”); and by al-Nasai, 7/178, through Sufyan, from al-Zuhri, from Ubayd Allah b. Abd Allah b. Utbah, who heard Ibn Abbas relate from Maymuna that a mouse fell into some butter and died. The Prophet, Allah bless him and grant him peace, was asked about it and said: “Remove it and what is around it, then eat the rest.”
In the Musnad of Ishaq b. Rahwayh—and, via his chain, in Ibn Hibban, no. 1364—the wording is: “If the butter is solid, remove what is around it and eat it; if it is liquid, do not approach it.”
This more detailed wording is also transmitted by Abd al-Razzaq in al-Musannaf, no. 278, by Abu Dawud, no. 3842, and by Ahmad, 2/232–233, 265, 490, all through Maʿmar, from al-Zuhri, from Saʿid b. al-Musayyib, from Abu Hurayra.
Ibn Hajar notes in Fath al-Bari that the reports from Maʿmar disagree: Ibn Abi Shayba related it from Abd al-Aʿla without the additional detail, whereas al-Nasai—through Abu al-Qasim from Malik—explicitly calls the butter “solid.” The same description appears in Ahmad’s version through al-Awzai, in al-Bayhaqi’s version through Hajjaj b. Minhal from Ibn Uyayna, and in Abu Dawud al-Tayalisi’s Musnad from Sufyan.
The extra wording found in Ishaq b. Rahwayh’s report from Sufyan is unique to him; the other meticulous transmitters from Sufyan—such as Ahmad, al-Humaydi, Musaddad, and others—do not mention it, and they regard Maʿmar’s version from al-Zuhri as erroneous.
Ibn Taymiyya records in al-Fatawa, 21/488, 502 that the hadith specialists agree Maʿmar often errs in his narrations from al-Zuhri, and he presents extensive evidence for this. Regarding the phrase “…then do not approach it,” he concludes that it is to be discarded.