The Messenger of Allah ﷺ forbade mixing ripe and unripe dates together to be drunk as a beverage, and that was the most common form of their intoxicating drinks on the day alcohol was prohibited.
إن رسول الله ﷺ نهى أن يخلط التمر والزهو ثم يشرب، وإن ذلك كان عامة خمورهم يوم حرمت الخمر.
Muslim narrated it in the Book of Drinks (1981) from Abu Tahir Ahmad bin Amr bin Sarh, who said, Abdullah bin Wahb told us, Amr bin Harith told me, that Qatada bin Diama told him that he heard Anas bin Malik say... and he mentioned it.