In the time of the Holy Prophet (PBUH) it was customary to consider prisoners of war as slaves. Any fighter who caught an enemy in war was regarded as the owner of that particular prisoner. As there were frequent wars between various tribes of Arabs the number of slaves captured used to be large. In fact there was no other system of handling this issue, there being no established government and only the tribal chiefs maintained some sort of governance, each tribe in its own way and based on its own traditions.

The prisoners-turned-slaves provided a cheap and controlled labour force, which was used as agricultural labour in the fields, as well as to perform other handyman jobs to meet the normal requirements of the tribal society. In fact they also provided a fighting force against subsequent enemy attacks.

If slavery were banned totally at the outset of Islam the socio-economic system would have collapsed. This is what happened to infrastructure of the societies on plantations in the southern parts of America during 18th century when slavery was banned. On the other hand, the resettlement of the freed black labour force could not be accomplished in a respectable manner for a long time and their social adjustment is still not satisfactory. Islam adopted a gradual approach to discourage and eliminate slavery. The way adopted was that for any act of religious omission or for commission of a wrong deed, the redemption was promised if a certain number of slaves were freed. The bigger the default the greater was number of slaves to be freed. Moreover, freeing a slave was considered an act of great charity earning high rewards in the life hereafter. In certain cases even the state paid the price to the master to buy the freedom of a slave. Also a slave could buy his freedom from his master by earning extra money to pay the master off. Thus, the slave population was expected to gradually decline, without disturbing the existing socio-economic fabric, ultimately leading to total abolition of slavery. And this is what actually did happen in practice.

The reduction in the number of salves also took place because in case of wars between various Muslim factions or tribes, the prisoners of war could not be made slaves.