Sahih Bukhari Volume 7, Book 69, Hadith Number 505.

Narrated By Anas : While I was serving Abu Talha. Abu Dujana and Abu Suhail bin Al-Baida’ with a drink made from a mixture of unripe and ripe dates, alcoholic drinks, were made unlawful, whereupon I threw it away, and I was their butler and the youngest of them, and we used to consider that drink as an alcoholic drink in those days.