Ata' bin Yasar (may Allah have mercy on him) said: Mu'awiyah bin Abi Sufyan (may Allah be pleased with them both) sold a vessel of gold or silver for more than its weight. Abu al-Darda' (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him): "He used to forbid the like of this, except equal for equal." Mu'awiyah (may Allah be pleased with him) said: I see no harm in this. Abu al-Darda' (may Allah be pleased with him) said to him: Who will excuse me regarding Mu'awiyah? I inform him from the Prophet (peace and blessings be upon him), and he informs me of his own opinion! I will not live with you in a land where you are. Then Abu al-Darda' (may Allah be pleased with him) came to Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) and mentioned this to him, so Sayyiduna Umar (may Allah be pleased with him) wrote to Mu'awiyah (may Allah be pleased with him) that he should not sell it except weight for equal weight. However, al-Rabi' did not mention, from Imam al-Shafi'i (may Allah have mercy on him), Abu al-Darda's coming to Sayyiduna Umar (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10494