[History] The Role of Islam in African Slavery (Pt 1)

"Although the law required owners to treat slaves well and provide medical treatment, a slave had no right to be heard in court (testimony was forbidden by slaves), had no right to property, could marry only with permission of their owner, and was considered to be a chattel, that is the (moveable) property, of the slave owner.

[...]

Slaves were obtained through conquest, tribute from vassal states (in the first such treaty, Nubia was required to provide hundreds of male and female slaves), offspring (children of slaves were also slaves, but since many slaves were castrated this was not as common as it had been in the Roman empire), and purchase. The latter method provided the majority of slaves, and at the borders of the Islamic Empire vast number of new slaves were castrated ready for sale (Islamic law did not allow mutilation of slaves, so it was done before they crossed the border)."

Africanhistory.about.com April 25, 2007 (follow link for pt2)