Musnad Abu Ya'la al-Mawsili 42:203

Abu Khaythama narrated to us, Jarir narrated to us, from al-A'mash, from Habib ibn Abi Thabit, from Abu Arta'ah, from Abu Sa'id, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade mixing raisins and dates, and [mixing] unripe dates (zahw) and dates.