وَأَوْفُوا۟ ٱلْكَيْلَ إِذَا كِلْتُمْ وَزِنُوا۟ بِٱلْقِسْطَاسِ ٱلْمُسْتَقِيمِ ۚ ذَٰلِكَ خَيْرٌ وَأَحْسَنُ تَأْوِيلًا
Wa awful kaila izaa kiltum wa zinoo bilqistaasil mustaqeem; zaalika khairunw wa ahsanu taaweelaa
Give full measure when you measure, and weigh with accurate scales: that is better and fairer in the end.
Give full measure when you measure, and weigh with an upright scale. That is better, and fairer in outcome.
Qistās is generally taken as a loanword rather than native Arabic, the name of a beam balance that reached Arabic from the Greek-speaking world, so the verse points at a specific instrument a trader of that time would have owned. It closes on ta'wīl, the word used elsewhere for interpreting a dream, meaning here how a thing finally turns out. Honest weighing sits in the same list as the covenant and the orphan's property.