Only children of slaves or non-Muslim prisoners of war could become slaves, never a freeborn Muslim. They also consider manumission of a slave to be one of many meritorious deeds available for the expiation of sins. According to Sharia, slaves are considered human beings and possessed of some rights on the basis of their humanity. In addition, a Muslim slave is equal to a Muslim freeman in religious issues and superior to the free non-Muslim.
In practice, slaves played various social and economic roles from Emir to worker. Slaves were widely employed in irrigation, mining, pastoralism and the army. Even some rulers relied on military and administrative slaves to such a degree that they seized power. However, people do not always treat with slaves in accordance with Islamic law. In some cases, the situation has been so harsh as to have led to uprisings such as Zanj Rebellion. However, this was usually the exception rather than the norm, as the vast majority of labour in the medieval Islamic world consisted of free, paid labour. For a variety of reasons, internal growth of the slave population was not enough to fulfill the demand in Muslim society. This resulted in massive importation, which involved enormous suffering and loss of life from the capture and transportation of slaves from non-Muslim lands. In theory, slavery in Islamic law does not have a racial or color component, although this has not always been the case in practice.
The Qur'an includes multiple references to slaves, slave women, slave concubinage, and the freeing of slaves. It accepts the institution of slavery. It may be noted that the word 'abd' (slave) is rarely used, being more commonly replaced by some periphrasis such as ma malakat aymanukum ("that which your right hands own"). The Qur'an recognizes the basic inequality between master and slave and the rights of the former over the latter.
The Qur'an also recognizes concubinage. A master may make his female slave as his concubine and, if she is a Muslim, he can marry her. Abstinence however is said to be a better choice. The Qur'an urges, without commanding, kindness to the slave and recommends, their liberation by purchase or manumission. The freeing of slaves is recommended both for the expiation of sins and as an act of simple benevolence. It exhorts masters to allow slaves to earn or purchase their own freedom (manumission contracts)."
Slaves are mentioned in at least twenty-nine verses of the Qur'an, most of these are Medinan and refer to the legal status of slaves. The legal material on slavery in the Qur'an is largely restricted to manumission and sexual relations. According to Sikainga, the Qur'anic references to slavery as mainly contain "broad and general propositions of an ethical nature rather than specific legal formulations.