who said, “Up to this very day I have never put black ink on white paper, and no man has ever narrated a single hadith to me without my committing it to memory.”
ʿAlī (ibn Khushram) added, “I conveyed this statement to Ishāq ibn Rāhwayh, whereupon he asked, ‘Are you amazed by that?’ I replied, ‘Yes.’ He said, ‘I never hear anything without memorizing it, and it is as though I am looking at seventy thousand hadith—or, he said, even more—laid out in my books.’
Abū Dāwūd al-Khaffāf said, ‘I heard Ishāq ibn Rāhwayh declare, “It is as though I can see one hundred thousand hadith in my books, and I am able to recite thirty thousand of them straight through.”’
He went on, ‘Ishāq dictated to us eleven thousand hadith purely from memory; then he read them back to us without adding a single letter or omitting one.’
This account was transmitted by the ḥāfiẓ Ibn ʿAdī from Yaḥyā ibn Zakariyyā ibn Ḥayyawah, who heard it from Abū Dāwūd, and he reported it in full.
By Allah, that is true memorization!
It is also related from Ishāq ibn Rāhwayh that he said, ‘I never heard anything without retaining it, and I have never memorized anything and then forgotten it.’
Abū Yazīd Muḥammad ibn Yaḥyā said, ‘I heard Ishāq say, “I know seventy thousand hadith by heart.”’
Aḥmad ibn Salamah reported: ‘I heard Abū Ḥātim al-Rāzī say, “I mentioned Ishāq ibn Rāhwayh’s phenomenal memory to Abū Zurʿah, and Abū Zurʿah replied, ‘No one has ever been seen with a sharper memory than Ishāq.’”’
Abū Ḥātim then added, ‘What is truly astonishing is the precision of his retention and his freedom from error in spite of the immense amount he memorized.’
I said to Abū Ḥātim, ‘He even dictated his tafsīr from memory.’
He replied, ‘That is all the more remarkable, for keeping track of the isnāds and texts of hadith is easier and lighter than preserving the chains and exact wording of tafsīr.’
Ibrāhīm ibn Abī Ṭālib, the ḥāfiẓ, said: ‘I once missed a session of Ishāq’s Musnad, which he was dictating from memory. I returned to him repeatedly, asking him to repeat it, but he was unable to oblige. So I made my way to him one day…’