What Abu Dharr was still doing decades later
He and his servant were wearing matching cloaks.
هُمْ إِخْوَانُكُمْ، جَعَلَهُمُ اللَّهُ تَحْتَ أَيْدِيكُمْ، فَمَنْ جَعَلَ اللَّهُ أَخَاهُ تَحْتَ يَدِهِ فَلْيُطْعِمْهُ مِمَّا يَأْكُلُ
Hum ikhwānukum, jaʿalahumu-Llāhu taḥta aydīkum. Fa-man jaʿala-Llāhu akhāhu taḥta yadihi fa-l-yuṭʿimhu mimmā yaʾkul
They are your brothers. Allah placed them under your hand. So whoever has his brother under his hand, let him feed him from what he eats.
Where this comes from
Someone suggested he take his servant's cloak and make a matching suit of it. He explained: he had once insulted a man about his mother, been told there was still ignorance in him, and had been dressing the man beside him identically ever since.
The full narration
Narrated Ma'rur:I saw Abu Dhar wearing a Burd (garment) and his slave too was wearing a Burd, so I said (to Abu Dhar), "If you take this (Burda of your slave) and wear it (along with yours), you will have a nice suit (costume) and you may give him another garment." Abu Dhar said, "There was a quarrel between me and another man whose mother was a non-Arab and I called her bad names. The man mentioned (complained about) me to the Prophet. The Prophet (ﷺ) said, "Did you abuse so-and-so?" I said, "Yes" He said, "Did you call his mother bad names?" I said, "Yes". He said, "You still have the traits of (the Pre-Islamic period of) ignorance." I said. "(Do I still have ignorance) even now in my old age?" He said, "Yes, they (slaves or servants) are your brothers, and Allah has put them under your command. So the one under whose hand Allah has put his brother, should feed him of what he eats, and give him dresses of what he wears, and should not ask him to do a thing beyond his capacity. And if at all he asks him to do a hard task, he should help him therein
Source
Ṣaḥīḥ al-Bukhārī · 6050
- Agreed upon as authentic (al-Bukhārī / Muslim)