Tirmidhi

Explanation:
1:
It is as if those male and female slaves who, along with worshipping the Lord of all worlds, also fulfill all the rights of their master well, for them there is a double reward: one for the worship of the Lord, and the other for fulfilling the rights of the master.

Hadith Commentary:
Where the Messenger of Allah (sallallahu alayhi wa sallam) has instructed masters to treat their male and female slaves well, there he has also expected from the slaves that, after fulfilling their Islamic obligations, they should consider the well-wishing of their masters to be an important duty, remain loyal to them, and not even entertain the thought of causing them harm.
If they act upon these teachings, they will receive a double reward from Allah.
The Messenger of Allah (sallallahu alayhi wa sallam) has praised such slaves, as is mentioned in the referenced hadith.
And Allah knows best.

Hadith Commentary: The meaning of Abu Hurairah radi Allahu anhu is that jihad is not obligatory upon a slave, and likewise, he cannot go for jihad or Hajj without his master's permission. Similarly, he cannot serve his mother with complete freedom. Therefore, if these matters were not present, I would prefer to remain someone’s slave rather than be free.

Ibn Battal said that this is from the statement of Abu Hurairah, and Dawudi and others have also said that it is interpolated (mudraj) in the hadith. Al-Isma‘ili has explicitly stated the interpolation from another chain through Abdullah ibn al-Mubarak with the wording: “By the One in Whose hand is the soul of Abu Hurairah...” and Muslim has also explicitly mentioned this.

(Commentary of Bukhari)

That is, this statement is from Abu Hurairah radi Allahu anhu. It has been explicitly reported from Abdullah ibn al-Mubarak, and this explicitness is also present in Muslim.

And Allah knows best.

Hadith Commentary:
➊
An objection is raised regarding this hadith: the noble mother of the Messenger of Allah (sallallahu alayhi wa sallam) passed away when the Messenger of Allah (sallallahu alayhi wa sallam) was still very young, so what is the meaning of being dutiful to one’s mother according to this hadith? The answer given is that the aforementioned statement is not from the Messenger of Allah (sallallahu alayhi wa sallam) himself, but rather it is the statement of Abu Hurairah (radi Allahu anhu), as is found in Sahih Muslim. The Messenger of Allah (sallallahu alayhi wa sallam) said:
“A righteous and pious slave receives a double reward.” And (Abu Hurairah said): “By the One in Whose hand is the soul of Abu Hurairah! If it were not for striving in the path of Allah, Hajj, and being dutiful to my mother being necessary, I would have wished to die as a slave.”
(Sahih Muslim, Al-Iman, Hadith: 4320(1665))
➋
The meaning of Abu Hurairah’s (radi Allahu anhu) statement is that jihad is not obligatory upon a slave, nor is Hajj included among his obligations, and he cannot serve his mother with complete freedom. Therefore, if these matters were not present, he would have preferred to remain a slave rather than be free.
(Fath al-Bari: 5/217)