Musnad Ahmad 31:691

'Affan narrated to us, Hammam narrated to us, Qatadah narrated to us, from Abu Nadrah, from Abu Sa'id al-Khudri: "The Prophet, peace and blessings of Allah be upon him, forbade making nabidh (a drink made by soaking fruit in water) from unripe dates and dried dates together, and from raisins and dried dates together."