Sahih Muslim Book 23, Hadith Number 4909.
Chapter : It is not approved to prepare Nabidh by mixing dry dates and grapes.
Abu Huraira reported that Allah’s Messenger (may peace be upon him) forbade (the preparation of Nabidh) from grapes and dates, and unripe dates and dry dates (by mixing them together). He (the Holy Prophet also) said: Prepare Nabidh from each one of them separately. This hadith has been narrated on the authority of Abu Huraira through another chain of transmitters.