Sahih Muslim Book 23, Hadith Number 4903.

Chapter : It is not approved to prepare Nabidh by mixing dry dates and grapes.

Isma’il b. Muslim al-‘Abadi reported on the authority of the same chain of transmitters: Allah’s Messenger (may peace be upon him) prohibited us that we should mix dry dates with unripe dates or (mix) grapes with dry dates (and prepare Nabidh). He also said: He who amongst you drinks-the rest of the hadith is the same.