Sayyiduna Umar (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "Whoever buys foodstuff should not sell it on until he has taken full possession of it (by measure)."
Abu Ya'la, al-Tabarani in al-Mu'jam al-Kabir, and al-Bazzar recorded it; its chain contains Abdullah bin Umar al-Umari, who has been criticised, though he has also been declared trustworthy.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6464