Sa'id bin al-Musayyib (may Allah have mercy on him) said: Sayyiduna Umar (may Allah be pleased with him) passed by Sayyiduna Hatib bin Abi Balta'ah (may Allah be pleased with him) while he was selling raisins in the market. Sayyiduna Umar (may Allah be pleased with him) said: "Either raise the price or leave our market." This is abridged; the complete hadith was narrated by Imam al-Shafi'i (may Allah have mercy on him). Al-Qasim bin Muhammad (may Allah have mercy on him) said: Sayyiduna Umar (may Allah be pleased with him) passed by Sayyiduna Hatib (may Allah be pleased with him) in the market of the Musalla (the Eid prayer ground), and in front of him were two baskets full of raisins. Sayyiduna Umar (may Allah be pleased with him) asked him their price, and he said: "I am giving two mudds for one dirham." Sayyiduna Umar (may Allah be pleased with him) said to him: "I have been told about a caravan coming from Ta'if, that they take your price as their reference. So either raise the price, or sell at home however you wish." Then, when Sayyiduna Umar (may Allah be pleased with him) came home and reflected, he went to see Sayyiduna Hatib (may Allah be pleased with him) at his house and said to him: "What I said to you was not a compulsion from me, nor was it a ruling from me; I said it only for the good of the people of the city. Now sell wherever you wish and sell at whatever price you wish."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11146