The only source in Islamic law that all Muslims accept indisputably is the Quran. And, conspicuously, the Quran decrees no earthly punishment for blasphemy — or for apostasy (abandonment or renunciation of the faith), a related concept. Nor, for that matter, does the Quran command stoning, female circumcision or a ban on fine arts. All these doctrinal innovations, as it were, were brought into the literature of Islam as medieval scholars interpreted it, according to the norms of their time and milieu.
Mustafa Skyol, Islam’s Problem With Blasphemy – NYTimes.com.