Lets see if your brain can process this.
http://www.askimam.org/fatwa/fatwa.php?askid=182a6760abb8a132392414c4be26ef57
QUESTION: What is the Islamic law with regard to slave-women? Was It permissible to have relations with these slave-women without a formal marriage ceremony?
It may, superficially, appear distasteful to copulate with a woman who is not a man's legal wife, but once Shariat makes something lawful, we have to accept it as lawful, whether it appeals to our taste, or not; and whether we know its underlying wisdom or not. It is necessary for a Muslim to be acquainted with the laws of Shariat, but it is not necessary for him to delve into each law in order to find the underlying wisdom of these laws because knowledge of the wisdom of some of the laws may be beyond his puny comprehension. Allah Ta'ala has said in the Holy Quran: "Wa maa ooteetum min al-ilm illaa qaleelan" which means, more or less, that, "You have been given a very small portion of knowledge". Hence, if a person fails to comprehend the underlying wisdom of any law of Shariat, he cannot regard it as a fault of Shariat (Allah forbid), on the contrary, it is the fault of his own perception and lack of understanding, because no law of Shariat is contradictory to wisdom.
Nevertheless, the wisdom underlying the permission granted by Shariat to copulate with a slave woman is as follows: The LEGAL possession that a Muslim receives over a slave woman from the "Ameerul-Mu'mineen" (the Islamic Head of State) gives him legal credence to have coition with the slave woman in his possession, just as the marriage ceremony gives him legal credence to have coition with his wife. In other words, this LEGAL POSSESSION is, in effect, a SUBSTITUTE of the MARRIAGE CEREMONY. A free woman cannot be 'possessed', bought or sold like other possessions; therefore Shariat instituted a 'marriage ceremony' in which affirmation and consent takes place, which gives a man the right to copulate with her. On the other hand, a slave girl can be possessed and even bought and sold, thus, this right of possession, substituting as a marriage ceremony, entitles the owner to copulate with her. A similar example can be found in the slaughtering of animals; that after a formal slaughtering process, in which the words, "Bismillahi Allahu Akbar" are recited, goats, cows, etc.; become "Halaal" and lawful for consumption, whereas fish becomes "Halaal" merely through 'possession' which substitutes for the slaughtering.
In other words, just as legal possession of a fish that has been fished out of the water, makes it Halaal for human consumption without the initiation of a formal slaughtering process; similarly legal possession of a slave woman made her Halaal for the purpose of coition with her owner without the initiation of a formal marriage ceremony.
In short, permission to have intercourse with a slave woman was not something barbaric or uncivilised; on the contrary, it was almost as good as a marriage ceremony. In fact, possession of a slave woman resembles a marriage ceremony in many ways and both have a lot in common with each other. One similarity is this that just as a free woman cannot have two husbands simultaneously, a slave woman cannot be used for intercourse by two owners. Another similarity is that a free woman whose marriage is on the rocks, cannot marry another man until her previous marriage is nullified through divorce, etc. Due to the discrepancies between husband and wife, the marriage sometimes reaches a stage where it becomes virtually impossible for the couple to live as man and wife with the result that divorce is brought into force to nullify marriage ties. Similarly, if a slave woman was married previously in enemy territory to a non-Muslim, and is then captured alone, i.e. without her husband, it is not permissible for any Muslim to have relations with her until her previous marriage is nullified, and that is done by bringing her to an Islamic country and making her the legal possession of a Muslim. Bringing her into Islamic territory necessitates the rendering of her previous marriage as null and void by Islamic law because with her husband in enemy territory and she in Islamic territory, it becomes virtually impossible for them to meet and live as man and wife. That is why it is not permissible to have intercourse with a woman whose husband is also taken into captivity and put into slavery with her. Another resemblance between the two is that, just as a divorcee has to spend a period called "Iddat" before another man is allowed to marry her, similarly, a slave woman has to spend a period called "Istibraa" before her owner can have coition with her.