It is based on the verses of the Quran and the Hadith's
(The Hadith, in Islam, is second in authority only to the Qur'an. The Hadith is a record of the prophet Mohammed's life, actions, and deeds. ...)
Google or Dog Pile search "Sharia", "Quran", and "Hadith" and you'll have a lifetime of reading to do.
Well, that is appropriate since anyone expousing its usage here should be bathed in pitch.