It is narrated from Sayyiduna Uthman bin Affan (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Do not sell one dinar for two dinars, nor one dirham for two dirhams."
Hadith Referenceموطا امام مالك رواية يحييٰ / كتاب البيوع / 1333