OCCASION OF REVELATION
Ebne Abbas says: When Prophet (SA) entered Medina, many people were involved in defraud in measuring. God revealed the above verses and warned them against this vice. They too accepted and stopped defraud in measuring.
It has been quoted in another narration: Many of people in Medina were merchant and defrauded in measuring and most of their transactions were Haram. The above verses were revealed and Prophet (SA) recited them for the people of Medina. Then, he added: five things against five things. People asked: What five things against what five things? He answered:
No people broke their promise unless God let their enemies dominate them! No people judged against divine order, unless poverty spread and increased among them!
No people engaged in prostitution, unless death rate increased among them!
No people defrauded in measuring, unless their agriculture was destroyed and famine stroke them! 
No people prohibited Zikat, unless rain was spared from them!

WOE TO THE DEFRAUDERS IN MEASURING
VERSES NO.1-6
It is remarkable that according to a narration from Imam Sadiq(AS): God has applied the term, Wail (Woe) just for the unbelievers, as it says in Mary:37: Woe to the unbelievers for the scene of a dreadful day.
It is induced from this narration that defraud in measuring is compared with disbelief!
Of course, the term defraud in measuring may be applicable to shortcoming in rendering services. For instance, when a worker or an employee reduces his efficient working hours, he would be an instance of defraud in measuring. Even any transgression from the divine boundaries and shortcoming in the social and moral relations could be included in this sort of defraud.
However, if they believed in the Day of Resurrection, and knew that all of their deeds are registered for judgment in that great court, they would never oppress and spoil people's rights.