Musnad Ahmad 830:151

'Abd al-Wahhab ibn 'Abd al-Majid al-Thaqafi narrated to us, from Ayyub, from Muhammad, and he mentioned a story in it. He said: When he arrived, 'Abd Allah was given a choice between thirty thousand and silver vessels. He said: So he chose the vessels. He said: Then merchants from Darin arrived, and he sold them to them for thirteen for every ten. Then he met Abu Bakrah and said: "Did you not see how I deceived them?" He said: "How?" So he mentioned that to him. He said: "I adjure you, or I swear upon you, that you must return them, for I heard the Messenger of Allah, peace and blessings of Allah be upon him, forbidding the likes of this."