Surah 55. Ar-Rahman, Ayah 9

To be taken both literally and figuratively. A man should be honest and straight in every daily matter, such as weighing out things which he is selling: and he should be straight, just and honest, in all the highest dealings, not only with other people, but with himself and in his obedience to Allah's Law. Not many do either the one or the other when they have an opportunity of deceit. Justice is the central virtue, and the avoidance of both excess and defect in conduct keeps the human world balanced just as the heavenly world is kept balanced by mathematical order.