Sahih Bukhari
Punishment of Disbelievers at War with Allah and His Apostle
Volume: 008 / Book Number: 082 / Hadith Number: 835
Narrated 'Abdullah bin 'Umar:
Those people who used to buy foodstuff at random (without weighing or measuring it) were beaten in the lifetime of Allah's Apostle if they sold it at the very place where they had bought it, till they carried it to their dwelling places.