I used to sell dates in the market. I would say, "I have measured this load of mine to be such-and-such," and I would hand over the loads of dates based on that measurement and take my profit. Something about this troubled me, so I asked the Messenger of Allah ﷺ about it.He said, "When you state the measurement, you must actually measure it out."
حدثنا علي بن ميمون الرقي حدثنا عبد الله بن يزيد عن ابن لهيعة عن موسى بن وردان عن سعيد بن المسيب
كنت أبيع التمر في السوق فأقول كلت في وسقي هذا كذا فأدفع أوساق التمر بكيله وآخذ شفي فدخلني من ذلك شيء فسألت رسول الله ﷺ فقال إذا سميت الكيل فكله
No references are available.
[Its chain is hasan] Ahmad reported it, 1/62, from Yahya bin Ishaq, who said, Ibn Lahia narrated to us, who said, Musa bin Wardan narrated to us, with the same wording. Yahya was among the early companions of Ibn Lahia, as noted in Tahdhib, 2/361. Hafs bin Hashim, may Allah have mercy on him, along with Ibn Mubarak and others, corroborated him, narrating it from Ibn Lahia with the same wording. It has a corroborating narration in Muslim, from the hadith of Ibn Umar, may Allah be pleased with both of them, with the same wording.