Surah 83. Al-Mutaffifin, Ayah 4

Legal and social sanctions against Fraud depend for their efficacy on whether there is a chance of being found out. Moral and religious sanctions are of a different kind. 'Do you wish to degrade your own nature?' 'Do you not consider that there is a Day of Account before a Judge Who knows all, and Who safeguards all interests, for He is the Lord and Cherisher of the Worlds? Whether other people know anything about your wrong or not, you are guilty before Allah'.