Sayyiduna Uqbah bin Amir al-Juhani (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "A Muslim is the brother of a Muslim. It is not lawful for a Muslim to sell goods and, if there is a defect in them, not to make it clear."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10734