﴿ وَإِذَا كَالُوهُمْ أَو وَّزَنُوهُمْ يُخْسِرُونَ ﴾

“but when they have to measure or weigh whatever they owe to others, give less than what is due!”

(But if they measure unto them) but when they measure for others (or weigh for them, they cause them loss) they decrease the measurement or the weight and behave very badly; it is also said that the above means: severe punishment on that day is unto the defrauders in the prayer, the poor-due, fasting and other acts of worship.