Musnad Ahmad 32:926

Yahya narrated to us, Humayd narrated to us, from Anas, who said: "I was serving Abu Ubaydah ibn al-Jarrah, Ubayy ibn Ka'b, Suhayl ibn Bayda', and a group of his companions at the home of Abu Talha. I was serving them until the drink had almost taken effect on them. Then a comer from the Muslims came and said: 'Do you not realize that wine has been prohibited?' They did not say: 'Until we look and ask.' Rather, they said: 'O Anas, overturn what remains in your vessel.' He said: 'By Allah, they did not return to it, and it was nothing but dates and unripe dates, and it was their wine on that day.'"