—a man whose prodigious memory could be weighed (1). I heard Abū Rajāʾ say:
“ʿUmar ibn Hārūn was extremely severe against the Murjiʾites; he would list their vices and afflictions, and because of that there was mutual enmity between them and him.
He was also among the most knowledgeable of people regarding the variant Qurʾānic readings; the reciters used to read to him and consult him about the different letters of the Qurʾān (2).”

I heard Abū Rajāʾ further relate:
“I asked ʿAbd al-Raḥmān ibn Mahdī, saying, ‘We have transmitted a great deal from ʿUmar ibn Hārūn, and it has reached us that you have spoken about him.’
He replied, ‘I seek refuge with Allah; I have said nothing about him except what is good.’
I said, ‘We have been told that you said he narrated from a certain person without having heard from him.’
He answered, ‘Glory be to Allah! I never said such a thing; and even if he had transmitted so, he is not considered suspect in our view (3).’”

ʿAlī ibn al-Ḥasan al-Hisanjānī (4) reported from Yaḥyā ibn al-Mughīra al-Rāzī, who said:
“I heard Ibn al-Mubārak criticize ʿUmar ibn Hārūn concerning his claimed audition from Jaʿfar ibn Muḥammad, even though ʿUmar reported about sixty ḥadiths from him.”

ʿAlī ibn al-Ḥusayn ibn al-Junayd said: “I heard Yaḥyā ibn Maʿīn declare, ‘ʿUmar ibn Hārūn is a liar; he arrived in Mecca after Jaʿfar ibn Muḥammad had already died, yet he went on to narrate from him.’ ”

Abū Ḥātim said: “Ibn al-Mubārak spoke against him, and thus his narrations were discarded (5).”

ʿAbd al-Raḥmān ibn Abī Ḥātim said: “I asked my father, ‘Abū Saʿīd al-Ashajj has narrated to us from ʿUmar ibn Hārūn.’ He replied, ‘His ḥadith is weak; Ibn al-Mubārak has disparaged him.’”