Bukhari

Hadith Commentary:
In the narration, the words "abd" (slave) and "sayyid" (master) have been used; this is precisely the objective of the chapter.

Hadith Commentary:
Where the Prophet (sallallahu alayhi wa sallam) instructed masters to show kindness and good treatment to their slave women and men, there he also explained to the slave women and men in the best manner that, after fulfilling their Islamic obligations, they should consider their important duty to be the well-wishing of their masters and bringing them benefit.
Masters and owners also have rights.
They should live their lives with loyalty towards them.
They should never even conceive of causing them harm.
If they do so, they will receive double the reward:
The reward for fulfilling Islamic obligations and the reward for serving their master. It was this concept of double reward upon which Abu Hurairah (radi Allahu anhu) expressed the desire that is mentioned in the next narration.

Hadith Commentary:
The aforementioned slave is given double reward because he fulfills two rights.
An objection arises here that, in this regard, the reward of the Sayyids would be less and that of the slaves would be more? The answer to this has been given in such a way that there is no harm in this.
It is also possible that the reward of the slaves is greater from this aspect, and the reward of the Sayyids is greater from other aspects.
This answer has also been given that, according to the hadith, preference is being given to that slave (‘abd) who fulfills both rights, as opposed to the slave who fulfills only one right; that is, in this, the reward of the slave is being compared to a slave like him, not to other free people.
The meaning of goodwill towards the master is that, in every situation, he intends the welfare and well-being of his master, and keeps the relationship free from betrayal and deception.
And Allah knows best.

Benefits and Issues:
A believing slave and subordinate should neither be stingy nor hesitant in speaking words of goodness to his master and superior; there is great reward in this.
And the master should also not turn up his nose or frown at the advice of the slave and servant.
Rather, he should look upon it with appreciation and reassurance, and, considering such a slave and servant to be his true well-wisher, treat him with kindness.
And he should deal with him with good conduct.
The command of Allah, the Exalted, is:
(hal jazā’ul-iḥsāni illā al-iḥsān) (al-Rahman, 60) — Is there any reward for good other than good?

Hadith Authentication: [وأخرجه البخاري 2546، ومسلم 43/1664، من حديث مالك به]
Jurisprudential Explanation:
➊ In Islam, previous forms of slavery are permitted, but encouragement is given to free slaves. In this way, slavery is gradually abolished.
➋ A person who is employed by someone (a Muslim) should always be engaged in the well-wishing and good conduct towards his master and superior, and should mold his life according to the Book and the Sunnah.
➌ The slave mentioned in the above hadith is superior to the free person who is negligent in obeying his master.
➍ Here is the mention of a noble slave and the good conduct of Ibn Umar radi Allahu anhuma towards him:
Once, Sayyiduna Ibn Umar radi Allahu anhuma went to some outlying villages of Madinah. When it was time to eat, he spread out the dining cloth with his companions. He saw a shepherd grazing sheep and called him, saying: "Come, eat with us." He replied: "I am fasting." Ibn Umar was greatly surprised and asked: "You are fasting in such heat?" He replied: "I consider these days (of life) as an opportunity for the life after death." Abdullah bin Umar (radi Allahu anhu) tested him by saying: "Sell us a sheep." He replied: "These sheep are not mine, but belong to my master."
Ibn Umar (as a test) said: "Tell your master that a wolf ate the sheep." The shepherd replied: "Then where is Allah?"—meaning, Allah is watching. Ibn Umar was so pleased that he bought the slave from his master and set him free, and also bought the sheep and handed them over to him. [تاريخ دمشق ملخصاً 33/89 وسنده حسن]