It is well known that the Koran allows a faithful Muslim up to four wives. What is not as well known is that he may also resort to "those that his right hand possesses" (i.e., slave girls captured in war or bought with money).
The fourth Surah (chapter) deals with women at some length. In it we read this:
Marry of the women, who seem good to you, two or three or four; and if ye fear that ye cannot do justice (to so many) then one (only) or (the captives) that your right hands possess (4:3)Apparently, the faithful may even resort to these slave girls if the girls are married.
And all married women are forbidden unto you save [except] those captives whom your right hands possess. It is a decree of Allah for you (4:24)And in Sura 23:1-6, we read this:
Successful indeed are the believers who are humble in their prayers, and who shun vain conversations, and who are payers of the poor-due; and who guard their modesty [i.e., abstain from sex]--save [except] from their wives or the slaves that their right hands possess, for then they are not blameworthy.