It is narrated from Hazrat Ata bin Yasar that Sayyiduna Muawiyah bin Abi Sufyan (may Allah be pleased with him) sold a drinking vessel made of gold or silver for more gold or silver than its weight. So Sayyiduna Abu Darda (may Allah be pleased with him) said to him: I heard the Messenger of Allah (peace and blessings of Allah be upon him) forbidding this, except that he permitted selling it equal for equal. Sayyiduna Muawiyah (may Allah be pleased with him) said: I do not see any harm in it. Sayyiduna Abu Darda (may Allah be pleased with him) said: Who will accept my excuse if I give Sayyiduna Muawiyah (may Allah be pleased with him) an answer? I am narrating to him the hadith of the Messenger of Allah (peace and blessings of Allah be upon him), and he is telling me his own opinion. Now I will not stay in your land. Then Sayyiduna Abu Darda (may Allah be pleased with him) came to Madinah to Sayyiduna Umar (may Allah be pleased with him) and related this incident to him. Sayyiduna Umar (may Allah be pleased with him) wrote to Sayyiduna Muawiyah (may Allah be pleased with him) that do not make such a sale again, except by weighing equal for equal.