The spread of this faith over so vast a portion of the globe is due to various causes, social, political and religious: but among these, one of the most powerful factors at work in the production of this stupendous result, has been the unmerited labours of Muslim (summoners /missionaries/ da’i) who, with the Prophet himself as their great example, have devoted their lives for the conversion of unbelievers. The duty of dawn is no after-thought in the history of Islam. Rather it was enjoined on believers from the beginning, as may be judged from the following passages in the Quran, which are here quoted in chronological order according to the date of their being delivered.