Musnad Ahmad 1060:15

Yahya ibn Ghaylan narrated to us, Rashdin narrated to us, Amr ibn al-Harith informed me, from Bukayr, from Abu Ishaq, the freed slave of Banu Hashim, that he narrated to them that they mentioned one day what [beverages] are steeped in, and they disputed regarding the gourd. Abu Ayyub al-Ansari passed by them, so they sent a person to him. He said: "O Abu Ayyub, is the gourd steeped in?" He said: "I heard the Messenger of Allah, peace and blessings of Allah be upon him, forbidding every pitch-coated vessel in which [beverages] are steeped." So he [the man] retorted to him regarding the gourd, and Abu Ayyub repeated his first statement to him.