What is the meaning of freeing a slave?

Question: The freeing of a slave has become a point of confusion for some people, so they do not know its meaning; perhaps because they have not seen it in practice.
Here, a brother is asking about freeing a slave? We hear about many expiations that require freeing a slave, but we do not know what a slave is? Is it a person sentenced to death who is then pardoned? Or is it an animal?

Answer: By freeing a slave, it is meant: freeing a male or female slave. Allah (Glorified and Exalted is He) prescribed for His servants that if they fight the enemies of Islam and overcome them, their offspring and women become slaves owned by the Muslims; they use them, benefit from them, sell them, and dispose of them as they wish.
Likewise, if prisoners are taken from them, the one in authority has the choice: if he wishes, he kills the prisoners, and if he wishes, he frees the prisoners—if he sees a benefit in releasing them—and if he wishes, he enslaves them, making them war spoils, and if he wishes, he kills them—if he sees a benefit in killing—and if he wishes, he ransoms them, if there are Muslim prisoners among the disbelievers, he takes the Muslim prisoners from the polytheists and gives them their prisoners; that is, exchanging prisoners, or he takes money from them to release their prisoners, as the Messenger (peace and blessings be upon him) did on the day of Badr; he (peace and blessings be upon him) had prisoners, some of whom were killed, and some were ransomed. Among them were al-Nadr ibn al-Harith and 'Uqbah ibn Abi Mu'ayt, whom he killed after the battle ended, and the rest were ransomed. He ordered the Muslims to ransom them, taking the ransom from the polytheists in exchange for releasing their prisoners, and he (peace and blessings be upon him) pardoned some of them.
So, pardoning is permissible for the one in authority—if he sees a benefit—and killing is permissible for him—if he sees a benefit—and enslaving is permissible for him—if he sees a benefit—and ransoming is permissible for him.
These are the slaves owned by the Muslims when they overcome their enemy; these become slaves to the Muslims, and after that, the owner of the slave has the choice: if he wishes, he uses him for his needs, and if he wishes, he sells him and benefits from the price. And if he wishes, he frees him for the sake of Allah (Glorified and Exalted is He) , which is a voluntary act, or he frees him as an expiation; such as the expiation for killing, or the expiation for intercourse in Ramadan, or the expiation for zihar, or the expiation for an oath. And the Prophet (peace and blessings be upon him) said: .