Musnad Ahmad 27:643

Isma'il narrated to us, Ayyub informed us, from Nafi', from Ibn 'Umar, who said: I arrived at the people while the Messenger of Allah (peace and blessings of Allah be upon him) had finished the sermon. I said: "What did the Messenger of Allah (peace and blessings of Allah be upon him) stand for?" They said: "He forbade the *muzaffat* (pitch-coated vessels) and the *duba'* (gourd vessels)."