اشتكى علي ا الناس، قال: فقام رسول الله صلى الله عليه وسلم فينا خطيبا، فسمعته يقول: أيها الناس لا تشكوا عليا، فوالله إنه لأخيشن في ذات الله أو في سبيل الله.
(Abu Sa’id al Khudri narrates) the people complained about ‘Ali. The Messenger of Allah stood up and delivered a khutbah (sermon). I heard him saying, “O people! Do not complain about ‘Ali. For, by Allah, he is scrupulous (i.e. he does not make concessions for anyone) regarding the matters of Allah’s (religion), or in the path of Allah.”
Imam Ahmed narrates this hadith via ibn Ishaq—in his (famous) sirah (biography of the Prophet salla Llahu ‘alayhi wa sallam). He says: “‘Abdullah ibn ‘Abdul Rahman ibn Ma’mar ibn Hazm narrated to me — from Sulaiman ibn Muhammad ibn Ka’b ib ‘Ujrah — from his aunt Zainab bint Ka’b, she was near Abu Sa’id al Khudri — from Abu Sa’id al Khudri.
There is a difference of opinion regarding whether Zainab bint Ka’b is a Companion or not. Ibn Hibban deems her reliable. She is the wife of Abu Sa’id al Khudri.
Ibn al Mulaqqin states:
As for Zainab, we have previously mentioned Ibn al Qattan’s opinion that she is reliable. Ibn Hibban deemed her reliable, for he mentioned her in his work on reliable narrators (Kitab al Thiqat). In fact, Ibn Fathun and Abu Ishaq ibn al Amin declared her among the Sahabah. Therefore, the hadith is authentic. And all praise is for Allah.
I say (i.e. the author): The biographical writers on the Sahabah such as ibn Fathun, ibn al Amin, and others merely make mention of anyone they might have come across who narrates a hadith, without taking into consideration the authenticity of the actual hadith. If the chain of transmission is inauthentic, then (in this case) suhbah (companionship) has not been established. However, if it is established that she is in fact the wife of Abu Sa’id al Khudri radiya Llahu ‘anhu, then, she too will be a Sahabiyyah (in most cases). Therefore, to deem this chain of transmission as Hassan (good) is not farfetched. Al Albani mentioned this hadith in his collection on authentic hadiths.
 Imam Ahmed: Musnad Ahmed, 3/86 and Fadaʾil al Sahabah, hadith no. 1161.
 Ibn al Mulaqqin: al Badr al Munir, 8/249.
 Al Albani: Silsilat al Ahadith al Sahihah, hadith no. 2479.