Musnad Ahmad 1012:59

Yahya ibn Sa'id narrated to us, from Isma'il—meaning Ibn Abi Khalid—, Hakim ibn Jabir narrated to us, from 'Ubadah ibn al-Samit, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Gold for gold, and silver for silver, like for like," until he specified salt. Mu'awiyah said: "This does not say anything to 'Ubadah." 'Ubadah said: "I, by Allah, do not care if I am not in a land where Mu'awiyah is. I bear witness that I heard the Messenger of Allah, peace and blessings of Allah be upon him, say that."