Musnad Ahmad 31:851

Rawh narrated to us, he said: Ash'ath narrated to us, from al-Hasan, from Abu Sa'id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) forbade the *duba'* (gourd), the *naqir* (hollowed-out log), and the *muzaffat* (pitch-coated vessel). And he said: "Prepare your nabidh (drink) in your waterskin and tie its mouth."