Sayyiduna Anas (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) said: "Al-mazah is forbidden, al-mazah is forbidden." Mazah means making nabidh by mixing unripe dates, ripe dates and raisins.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17460