Ḥajjāj ibn Muḥammad transmitted—from Ibn Jurayj—who said: Abū Ḥarb ibn Abī al-Aswad related to me, from his father.

Ibn Jurayj then added—together with another man transmitting from Zādhān—that they said:
“When ʿAlī was asked about Abū Dharr, he replied: ‘He absorbed knowledge that proved too weighty for him to convey. He was fiercely protective of his religion, keen on learning, constantly questioning, yet unable to disclose the knowledge he possessed.’ (1)

Sulaymān ibn al-Mughīrah narrated—from Ḥumayd ibn Hilāl—who said that ʿAbd Allāh ibn al-Ṣāmit told us:
‘I entered with Abū Dharr, along with a group from Ghifār, to see ʿUthmān through a door by which people would not normally approach him—he said, “and we feared how ʿUthmān might react toward him.” When Abū Dharr reached him, he greeted him with salām, and before saying anything else declared:
“Do you think I am one of them, O Commander of the Believers? By Allah, I am not one of them, nor can I equal them!”
He then asked permission to withdraw to al-Rabadhah. (2)

Yaḥyā ibn Salamah ibn Kuhayl reported—from his father, from Abū Idrīs, from al-Musayyab ibn Najabah, from ʿAlī—that he was asked, “Tell us about the Companions of Muḥammad ﷺ; tell us about Abū Dharr.” He replied:
‘He learned knowledge, then fastened it up with a very tight knot.’ (3)

Abū Isḥāq narrated—from Hāniʾ ibn Hāniʾ—that he heard ʿAlī say:
‘Abū Dharr was a vessel filled with knowledge, sealed shut; nothing of it spilled out until he died.’

From Abū Salamah—mursal:
The Prophet ﷺ said, “O Allah, forgive Abū Dharr and turn toward him in mercy.”

A report is also attributed to the Prophet ﷺ: “No prophet was ever sent except that he was granted seven close companions…”