The Reward Of Freeing Ten Slaves With 1 Dua
During the time of the Prophet Muhammad (peace and blessings be upon him), having a slave was like having a money bank. People considered themselves very lucky to own one, just as today…

During the time of the Prophet Muhammad (peace and blessings be upon him), having a slave was like having a money bank. People considered themselves very lucky to own one, just as today people feel rich if they have money, cars, and big houses.
Now here our religion (Islam) has given us many privileges, one of which is that if any person recites this Dua a hundred times in a day, he gets the reward of freeing ten slaves, A hundred good deeds are written (Angel Register) in it and a hundred bad deeds will be erased with it. This word will become a protection from sheetan until the evening and no one’s deed will be better than it except the one who did more than it.
(Sahih Bukhari 3293, Sahih Muslim 2691)
What does Islamic law say about slaves?
Slavery was not introduced by Islam; it was a widespread practice for centuries, even in the West. Many religions did not talk about the rights of slaves, Islam addressed the rights of slaves and significantly improved their status in society.
’’فَإِذا لَقِیْتُمُ الَّذِیْنَ کَفَرُوا فَضَرْبَ الرِّقَابِ حَتَّی إِذَا أَثْخَنتُمُوھُمْ فَشُدُّوا الْوَثَاقَ فَإِمَّا مَنّاً بَعْدُ وَإِمَّا فِدَاء حَتَّی تَضَعَ الْحَرْبُ أَوْزَارَھَا.‘‘(محمد:4)
So when you meet the disbelievers (in battle), strike (their) necks until you have thoroughly subdued them, then bind them firmly. Later (free them either as) an act of grace or by ransom until the war comes to an end. So will it be. Had Allah willed, He (Himself) could have inflicted punishment on them. But He does (this only to) test some of you by means of others. And those who are martyred in the cause of Allah, He will never render their deeds void.
In hadith, Prophet Muhammad SAW Said: Allah will quarrel with three people on the Day of Resurrection, one of them is There will be one who will make a free Muslim slave then they sell them.