Muslims are told to live in the way of Muhammad by Sunnah and hadith. Muhammad was a slave owner and trader.  Muhammad  captured slaves in battle. Muhammad had sex with his slaves (One such example is Maria al-Qibtiyya ).  Muhammad instructed his men to do the same as he did regarding female slaves. List of Muhammad's Wives and Concubines: http://wikiislam.net/wiki/List_of_Muhammads_Wives_and_Concubines