Musannaf Ibn Abi Shayba 13:2874

Abu Bakr narrated to us, he said: Abdullah ibn Idris narrated to us, from Hisham, from Ibn Sirin and al-Hasan, that they were both asked about a man who buys food and sells it by its measure. They said: "No, not until the two measures (the measure of the seller and the measure of the buyer) have passed through it, so that the increase belongs to him and the decrease is upon him."