Emancipating slaves in Islam

Islam did abolish slavery gradually in a way that guarantee the safety of society against social troubles, In the Arabian peninsula trade and agriculture depended mainly on the work of slaves. Some people traded in slaves. So, to avoid revolution or insurgence, Islam did succeed in abolishing slavery and even dried its source.

we can condense the ways in which Islam abolished slavery as follows:

(1)Islam has made freeing slaves an act of righteousness

A Muslim who frees his slave will have a shield against the hell fire. The prophet says : "Whichever man frees a Muslim man, Allah ta'ala will liberate for each of his organ an organ from the Fire"

(2)Punishing a slave severely is atoned by freeing him.
Prophet Mohammed says "Whoever slaps his slave or strikes him, his atonement (kaffara) is to free him."

(3)Relative slaves is to freed at once, islam is emphatic about fostering the relationship between the persons and his relatives.

(4) Killing a believer accidently entails setting a slave free to be atoned
Allah (swt) says: "Never should a believer kill another believer, except by mistake. If anyone kills a believer by mistake he must free one Muslim slave …." [4:92]
(5) breaking an oath is to be atoned by freeing a slave

Allah (swt) says: "Allah does not take you [to task] for what is thoughtless in your oaths, only for your binding oaths: the atonement for breaking an oath is to feed ten poor people with food equivalent to what you would normally give your own families, or to clothe them, or to set free a slave." [5:89]

(7) Whoever says to his wife ‘you are to me like my mother's back' and then returns to her, his atonement is freeing a slave.

Allah (swt) says:
"Those of you who say such a thing to their wives (i.e. ‘you are to me like my mother's back'), then go back on what they have said, must free a slave before the couple may touch one another again." [58:3]

(8) Whoever invalidates the fast of Ramadan by sexual intercourse is to be atoned by freeing a slave

It is narrated that someone came to the prophet asking what to do after he had sexual intercourse with his wife in Ramdan, the month of fasting. The prophet ordered him to free a slave.

(9) A slave can free himself by a manumission contract.

A slave can make an agreement with his master of setting him free after paying a certain amount of money, also the slave holder should help him by money.

Allah (swt) says:

"If any of your slaves wish to pay for their freedom, make a contract with them accordingly, if you know they have good in them, and give them some of the wealth Allah has given you." [24:33]
(10) The state treasury is to spend on freeing slaves
Allah (swt) says:
"Alms are meant only for the poor, the needy, those who administer them, those whose hearts need winning over, and for (riqab) and helping those in debt, for Allah's cause, and for travellers in need. This is ordained by Allah; Allah is all knowing and wise." [9:60]

His (swt) statement: "and for (riqab)" means freeing slaves.