the scholar Aḥmad Shākir (may Allāh have mercy on him) said in his commentary on "al-Tirmidhī" (2/277): "It is as if al-Tirmidhī is indicating a weakness in the isnād of the ḥadīth because the narrators transmitted it from Isrāʾīl from Abū Isḥāq, and that it was only narrated from al-Thawrī by Abū Aḥmad; however, this is not a defect if the narrator is trustworthy. There is no harm in the ḥadīth being from both al-Thawrī and Isrāʾīl from Abū Isḥāq, and Abū Aḥmad is trustworthy. His narration from al-Thawrī strengthens the narration of others from Isrāʾīl, and he also narrated it from Isrāʾīl like others, so he preserved what others preserved and added what they did not know, or what was not narrated to us from them." I said: And this is the investigation required by the science of ḥadīth. Moreover, it can be added to this and to al-Tirmidhī the narration of ʿAbd al-Razzāq from Sufyān al-Thawrī, and this supports the investigation of Aḥmad Shākir (may Allāh have mercy on him). He missed the extraction of the ḥadīth of Isrāʾīl from Abū Isḥāq—who is the second of his three companions previously mentioned—so I say: the second is Isrāʾīl—who is Ibn Yūnus ibn Abī Isḥāq al-Sabīʿī—who said: from Abū Isḥāq with it, and in it is the addition. It was recorded by Aḥmad (2/24, 58, 77, 99), and al-Ṭaḥāwī in "Sharḥ al-Maʿānī" (1/176) from his paths—one of them with Aḥmad in the third place: narrated to us by Muḥammad ibn ʿAbd Allāh ibn al-Zubayr, who is Abū Aḥmad al-Zubayrī. The third: Abū al-Aḥwaṣ Salām ibn Sulaym said: from Abū Isḥāq with it, and in it is the addition in the wording: I heard the Prophet (ṣallá Allāhu ʿalayhi wa-sallam) more than twenty times recite ... the ḥadīth