Musnad Ahmad 30:1815

Muhammad ibn Idris narrated to us, Malik informed us, from Musa ibn Abi Tamim, from Sa'id ibn Yasar, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "A dinar for a dinar, and a dirham for a dirham; there is no superiority between them."