سورة هود

The Prophet (peace be upon him and his family): There are five things — if you are afflicted with them, seek refuge in Allah [from their evil]... [short-selling]: do not reduce measures and scales, for [otherwise] you will be afflicted with famine, drought, hardship of livelihood, and the tyranny and oppression of the rulers.

The Prophet (peace be upon him and his family): When measure and scale are given short, Allah afflicts them with years of famine, drought and a decrease in produce.

Imam Baqir (peace be upon him): Jabir (may Allah have mercy on him) narrates from Imam Baqir (peace be upon him): Amir al-Mu'minin (peace be upon him) among you in Kufa would come out of the Dar al-Imara (governor's residence) every morning and go round the markets of Kufa one by one, with a whip which had two ends and was called "al-Sabiba" upon his shoulder. He would stop at every market and call out among its people: "O company of merchants! Fear Allah the Mighty and Majestic." When they heard his voice, they would drop what was in their hands and give their hearts and souls to his words, listening with their ears as he said: "Put seeking good from Allah before [your dealings], seek blessing through easy-going conduct in your transactions, be accessible to buyers (do not sell dear so they flee from you), adorn yourselves with the ornament of forbearance, refrain from swearing oaths, keep away from lying, avoid injustice, deal fairly with the wronged, do not go near usury, وَ أَوْفُوا الْکَیْلَ وَ الْمِیزَانَ [and give full measure and weight (do not give short measure)] (Al-An'am/152), وَ لا تَبْخَسُوا النَّاسَ أَشْیاءَهُمْ وَ لا تَعْثَوْا فِی الْأَرْضِ مُفْسِدِینَ [and do not defraud people of their things and do not act corruptly in the land, making mischief]." He would go round all the markets of Kufa, then return and sit to attend to the people's affairs.