Islam is both belief and legislation which organizes all the relationships of man. Belief is the basis of the code of laws and the code of laws is the result of belief, for legislation without belief is a building without a foundation -- and belief without a code of laws to put it into effect would be merely theoretical and ineffective. Thus, in Islam there is an intimate interrelation between belief and the code of laws governing all conduct, and those who deny this can by no means be considered to be Muslims...
Islamic law has clearly stated the obligations of the Muslims in all areas of life and the penalties to be inflicted for offenses and irregularities...
Thus in Islam we find no distinction in community life between that which is called religious and that which is outside religion. In Islam religion is concerned with faith and worship, and also with the upbringing, education, and guidance of the people, and with all economic and social dealings as to those which are legitimate and illegitimate, sound or corrupt; and religion is concerned with the government of the people and the administration of state machinery, with the operation of all the functions of the community or nation.
Islam -- The Straight Path: Islam Interpreted by Muslims